Important topics and their relevance in UPSC CSE exam for May 31, 2026. If you missed the May 30, 2026, UPSC CSE exam key from the Indian Express, read it here.Preliminary Examination: Current events of national and international importance.Mains Examination: General Studies-II, III: Bilateral, regional and global groupings and agreements involving India., Science and Technology, indigenization of technology and developing new technology.What’s the ongoing story: In the first official confirmation of India selling the BrahMos missiles to Vietnam, Defence Secretary Rajesh Kumar Singh said Saturday that a deal has been signed with the southeast Asian nation for the supply of the missiles, adding that a similar deal with Indonesia is in “final stages”. Key Points to Ponder:— BrahMos missile: Know the background and history development.— What are the key features of the BrahMos missile?— What is the strategic significance of BrahMos?— What are the different versions of BrahMos?— The BrahMos missile is named after which two rivers?— What are cruise missiles?— Know the terms and differences between infrasonic, subsonic, supersonic, ultrasonic, etc.— What do you understand by stealth technology?— What are India’s important precision-guided long-range weapons and drones?— What are the major defence agreements of India in the recent past?Key Takeaways:Story continues below this ad— Singh, who is in Singapore to attend the Shangri-La Dialogue, made the comments in response to a question on potential buyers of the missile system.— “My understanding is that with both Indonesia and with Vietnam, the deal is in the final stages… In fact, for Vietnam, I understand that it has already been signed, probably not publicly announced, but it’s already been signed,” he said.— Signing a contract worth nearly 375 million dollars, The Philippines had become the first foreign buyer of the BrahMos missile system from India in 2022. In March, Indonesia had also said that it had entered into an agreement with India to procure the BrahMos missile system.— The details of the deals with Indonesia and Vietnam are yet to be made public. Singh said countries generally sell sophisticated weapon systems and platforms to nations they regard as friendly partners.Story continues below this ad— He said India has a strong commitment to the ASEAN nations, adding: “…we treat all of you as ‘friendly foreign countries’ with whom we can share advanced defence technologies”.— He told delegates that India was ready to work with partners across the region and beyond to build resilient supply chains and trusted defence partnerships besides securing maritime commons.— He said India had undertaken major reforms in defence production, innovation and exports over the past decade, adding that the sector had been opened to greater private-sector participation. Do You Know:— BrahMos supersonic cruise missiles, which have been operationalised in all three defence services, are built by BrahMos Aerospace, a joint venture between India’s Defence Research and Development Organisation (DRDO) and Russia’s NPO Mashinostroyeniya.Story continues below this ad— BrahMos is a two-stage missile with a solid propellant booster engine. Its first stage brings the missile to supersonic speed (meaning faster than sound) and then gets separated. The liquid ramjet or the second stage then takes the missile closer to three times the speed of sound in cruise phase. The missile has an extremely low radar signature, making it stealthy, and it can follow a variety of paths. — BrahMos missiles operate at close to Mach 3 speed in the cruise phase, which ensures reduced flight time, lower dispersion of targets, and quicker engagement time and non-interception.— The missile operates on a ‘Fire and Forget Principle’, adopting varieties of flights on its way to the target. As per its website, cruising altitude could be up to 15 km and terminal altitude as low as 10 metres. The missile carries a conventional warhead weighing 200-300 kg.— The range of some BrahMos missiles for land and ship attacks have been nearly doubled in recent years.Other Important Articles Covering the same topic:Story continues below this adOperation Sindoor: From HAMMER to BrahMos, the precision guided long range weapons in Indian military’s arsenalUPSC Prelims Practice Question Covering similar theme:(1) With reference to the BrahMos missile, consider the following statements:1. It is a two-stage missile with a solid propellant booster engine.2. The missile has a very low radar signature which makes it stealthy.Story continues below this ad3. The course of the missile cannot be altered once fixed.4. There is no sea to sea variant of BrahMos missile.How many of the statements given above are correct?(a) Only one(b) Only two(c) Only three(d) All fourALSO READ | Knowledge Nugget | What is Retrospective Taxation? Explained through SC’s Online Gaming GST VerdictFRONT‘No China hegemony, India critical anchor, helps maintain balance of power’Syllabus:Mains Examination: General Studies-II: Effect of policies and politics of developed and developing countries on India’s interests, Bilateral, regional and global groupings and agreements involving India. Story continues below this adWhat’s the ongoing story: In an expansive articulation of American strategic intent in the Indo-Pacific, US Defence Secretary Pete Hegseth Saturday described India as a “critical anchor” to “hold the line” in South Asia and that a “powerful” India, acting in its own self-interest, “advances our shared goal of maintaining a balance of power across the region.” Key Points to Ponder:— What is Shangri La Dialogue?— What do you understand by the term ‘balance of power’ in international relations? — What is the Indo-Pacific? What is its relevance in contemporary global geopolitics?— What is the history of India-US relations? — What are the areas of cooperation between India and the US?— How have India-US defence relations evolved? Story continues below this ad(Thought Process: Know about the Basic Exchange and Cooperation Agreement for Geospatial Intelligence (BECA), Logistics Exchange Memorandum of Agreement (LEMOA), Communication Compatibility and Security Agreement (COMCASA), and General Security of Military Information Agreement (GSOMIA).)— Where does India stand in the US Indo-Pacific strategy?— What are the challenges to India-US bilateral ties?— Read about India’s SAGAR policy.Key Takeaways:— Speaking at the Shangri La Dialogue in Singapore Saturday, he framed the balance of power in Asia as one “in which no state, including China, can impose its hegemony and hold the security or prosperity of our nation and our allies in question.”— At the same time, though, he struck a softer note on Beijing saying Washington was not seeking confrontation despite concerns over China’s military build-up. And that under US President Donald Trump, US-China relations were “better than they’ve been in years.”— Hegseth noted India’s modernisation of its military to bear its share of the security burden, particularly in the Indian Ocean, and praised its efforts to build “heavy industrial and logistics capacity to sustain high-end military operations, including the ability to repair and maintain shared platforms and support US Navy vessels operating forward in the theatre.”— The Defence Secretary announced that the US had committed to pursuing “co-production” of Javelin anti-tank guided munitions with India — “real, tangible steps to improve the collective readiness of our forces.” Defence co-production of this kind, with a sophisticated frontline weapon system, is framed as deepening the bilateral defence relationship.— Highlighting that Washington’s broader Indo-Pacific strategy was aimed at preserving regional stability while ensuring that no single power could dominate the region, he said: “What we seek … is a genuinely stable equilibrium that works for Americans as well as for our allies.”— He added that the Indo-Pacific remained central to US security and prosperity, underlining that Washington remained committed to the region despite security challenges elsewhere, including in West Asia.— The US would continue to strengthen military capabilities and cooperation with allies to preserve regional stability, he said, adding that defence commitments have been undertaken by several Indo-Pacific partners, including India, Japan, South Korea, Australia, Singapore, Malaysia, Thailand, Vietnam and the Philippines. Do You Know:— Indo-Pacific: The Indo-Pacific is a geographical area that encompasses the regions of the Indian Ocean and the Pacific Ocean, along with the countries surrounding them and the crucial waterways and marine resources. It also includes critical maritime chokepoints such as the Strait of Malacca, Taiwan Strait, the Bab-al-Mandeb, Straits of Lombok and Sunda, the South China Sea, etc., which are vital for global trade and energy supply routes. — However, the extent of what constitutes the Indo-Pacific or the geographical definition of the “Indo-Pacific” varies from state to state.— Balance of power: The term balance of power indicates the relative distribution of power among states into equal or unequal shares. Inequality and potential for violence, which characterise the international system, encourage states to maintain and preserve equilibrium: dominant states guard against potential challengers, while others form an alliance to restrain a potential hegemonic state. Other Important Articles Covering the same topic:Hegseth backs bigger India role in Indo-Pacific, says US Navy vessels to get support The Indo-Pacific: A strategic arena for India’s global influenceBeyond Trending: What is balance of power?Previous year UPSC Mains Question Covering similar theme:‘What introduces friction into the ties between India and the United States is that Washington is still unable to find for India a position in its global strategy, which would satisfy India’s National self-esteem and ambitions’. Explain with suitable examples. (UPSC CSE 2019) NATIONWhy Supreme Court is cracking the whip against states over ChambalSyllabus:Preliminary Examination: Current events of national importance and environment ecology.Mains Examination: General Studies-III: Conservation, environmental pollution and degradation.What’s the ongoing story: The Supreme Court’s latest indictment of Rajasthan, Madhya Pradesh and Uttar Pradesh over illegal sand mining in and around the inter-state National Chambal Gharial Sanctuary reflects years of judicial frustration with persistent administrative apathy, leading to an environmental and governance crisis. Key Points to Ponder:— Know about the Chambal river ecosystem in detail.— What is the ecological significance of the Chambal River ecosystem?— How has illegal sand mining become a major threat to Chambal river ecosystems and its biodiversity?— How does illegal mining present a challenge to the rule of law and environmental governance in India?— Know about the important species of the Chambal river ecosystem: Gharial, Gangetic Dolphin, Indian Skimmer, Sarus Crane, and Red-crowned Roofed Turtle.— Know about the National Chambal Gharial Sanctuary in detail. — What steps should be taken for river conservation in India?Key Takeaways:— The apex court, which took suo motu cognizance of the matter in March, was particularly harsh on Rajasthan in its May 26 order, slamming its “wholly casual, indifferent and indolent” conduct, and rebuking the state administration for demonstrating “persistent inaction” and a “disturbing lack of seriousness”.— Sand mining was prohibited in the Chambal sanctuary in 2006 but illegal extraction has continued and flourished over the years under organised syndicates. The indiscriminate sand extraction has severely disrupted the Chambal’s riverine ecosystem, damaging aquatic habitats and threatening environmental flows, putting at risk the survival of endangered gharials, freshwater dolphins and turtles.— In 2012, an IPS officer was crushed to death by a tractor carrying illegally mined sand in Morena, Madhya Pradesh. The Court’s May 26 order referred to the killing of two forest guards this year alone – one again in Morena last month, and another in Dholpur, Rajasthan, this January – to emphasize what it called a “serious erosion of the rule of law” in the region. — At a hearing on May 14, the Supreme Court expressed concern that authorities appeared to prosecute only vehicle drivers, while failing to investigate the financiers, contractors, operators and masterminds controlling illegal mining syndicates. — The Court stressed that environmental governance could not remain dependent on repeated judicial intervention and authorities must ensure “sustained and proactive enforcement” to curb illegal mining in the Chambal sanctuary landscape.— On forest personnel allegedly lacking adequate weapons to counter heavily armed mining mafias, the Court said: “The State cannot be permitted to plead helplessness.”— Because of dark, foreboding myths around the Chambal – from a story linking its origins to a mountain of dripping leather, to the belief that Draupadi cursed its waters – the river, by all means mightier than the Yamuna, has remained one of India’s most pristine. No great cities or shrines came up on its banks, with the isolation later fostering the badland reputation of the Chambal ravines as a place where all manner of black sheep — rebel tribesmen and later bandits – found refuge.— The Chambal’s splendid isolation started to wane after people living in the arid districts of Rajasthan and Madhya Pradesh started moving into the region. By 1960, the first dam on the Chambal – Gandhi Sagar – was built on the Rajasthan-Madhya Pradesh border.— In the next five decades, six major irrigation projects – Rana Pratap Sagar, Jawahar Sagar and Kota barrage, Parbati Pick-up Weir, Harish Chander Sagar and Gudha dam – 12 medium, 134 minor and several panchayat-level projects came up in the Chambal basin. There are many more in the pipeline while work continues on several dozen.— Sand mining is an additional challenge. Since there is still no technology to use desert sand for construction, the pressure is entirely on riverbanks, reservoirs, and coasts.UPSC Weekly Concepts Snapshot | Energy storage technologies, Bond Yield and ENSO— Despite the threats to it, the Chambal still has the highest conservation value among rivers in the greater Gangetic basin. Its aquatic ecosystem and forest landscape support more than 550 species, it hosts the largest contiguous and most viable breeding populations of the critically endangered gharial and the red-crowned roofed turtle, and has one of the most important habitats of the Gangetic dolphin, Indian skimmer, black-bellied tern, sarus crane and a host of endangered turtle species.— Besides, the Chambal is a vital corridor for dispersal of wildlife in an otherwise fragmented forest landscape across more than a dozen national parks and sanctuaries, such as Ranthambore, Keladevi, Kuno-Palpur, Madhav and Darrah-Mukundra.Do You Know:— The Chambal River is a tributary of the Yamuna River in central India and thus forms part of the Gangetic river system. The river flows north-northeast through Madhya Pradesh, running for a time through Rajasthan, then forming the boundary between Rajasthan and Madhya Pradesh before turning southeast to join the Yamuna in the Uttar Pradesh state. — The Chambal river originates at Janapav, south of Mhowtown, near Manpur, Indore, on the south slope of the Vindhya Range in Madhya Pradesh. Its basin drains the Malwa Plateau, while its important tributary, the Banas River, originates in the Aravalli Range of Rajasthan. UPSC Prelims Practice Question Covering similar theme:(2) Consider the following statements with reference to the Chambal River ecosystem:1. The Chambal River is a tributary of the Yamuna and forms part of the Gangetic river system.2. The Banas River, an important tributary of the Chambal, originates in the Vindhya Range.3. Illegal sand mining in the Chambal region has adversely affected aquatic habitats and environmental flows.Which of the statements given above are correct?(a) 1 and 2 only(b) 1 and 3 only(c) 2 only(d) 1, 2 and 3 Learn through imageECONOMYDomestic solar cell mandate: How new rules may squeeze smaller manufacturersSyllabus:Preliminary Examination: Current events of national importance. Mains Examination: General Studies-II, III: Government Policies and interventions, indigenization of technology and developing new technology.What’s the ongoing story: Only locally manufactured solar cells can be used in domestic, commercial and industrial solar projects starting June 1, according to a Union government mandate. Key Points to Ponder:— How are solar panels manufactured?— What is the objective behind India’s new domestic solar cell mandate?— Why is domestic manufacturing of solar cells crucial for India’s clean energy transition and energy security?— What is the contribution of solar energy in India’s renewable energy? — What are the challenges faced by India’s solar manufacturing ecosystem?— What are the advantages of import substitution policies in strategic sectors?— What are the concerns associated with the new solar cell mandate?Key Takeaways:— Cells — components that convert sunlight into electricity — are the building blocks of solar modules, the panels used to generate power. This domestic cell sourcing mandate is aimed at reducing India’s dependence on imports and strengthening the domestic solar manufacturing ecosystem.— But it has also raised concerns. India has a large solar module manufacturing base, nearly 200 gigawatts (GW) per annum. But the manufacturing capacity of cells, the primary constituents of these modules, is far lower at around 30 GW. This means much of the module manufacturing capacity has been built upon imported cells. — The new move, therefore, could disproportionately affect smaller solar module manufacturers which, unlike larger companies, may not manufacture their own cells. Industry insiders have also raised concerns that the mismatch in cell and module manufacturing capacity could lead to potential market consolidation. — First, let’s understand how solar panels are manufactured. The process begins with polysilicon, which is processed into ingots. These ingots are sliced into wafers, which, in turn, are used to manufacture solar cells. These cells are subsequently assembled into modules, or panels.— Under the new mandate, all “net-metering” and “open access” solar projects commissioned after June 1 will have to use domestically manufactured solar cells. — Net-metering projects largely refer to rooftop solar installations — such as those under the PM Surya Ghar: Muft Bijli Yojana — where consumers can offset electricity bills by supplying surplus power back to the grid. — Open access projects mainly cater to commercial and industrial consumers procuring renewable energy directly from developers. — Although developers had sought an extension of the deadline, the government clarified on May 25 that there would be “no blanket” relief. Limited relaxations would instead be granted on a case-by-case basis for projects where module installation had already been completed or where developers have already made significant progress, such as land acquisition, connectivity arrangements or installation of solar modules.— The new mandate has sparked concerns among module manufacturers, particularly non-integrated players — those without internal cell manufacturing facilities. — Industry executives cautioned that such companies could face significant supply risks as they would now be forced to procure domestically manufactured cells from larger competitors that also operate in the module market, potentially creating an uneven playing field.— According to experts, the timing of the transition has added to the stress. India’s solar module manufacturers are currently grappling with overcapacity and weakening export opportunities amid steep US tariff barriers.— However, a divergent view is also emerging within the industry, with several manufacturers viewing the new mandate as a relief of sorts and offering a strong policy push for the investments being made in India’s domestic solar manufacturing ecosystem.— They maintain that concerns over limited domestic cell manufacturing capacity are overstated, especially because large utility-scale solar projects bid out before August 31, 2025 have been exempted from the domestic sourcing requirement for solar cells. According to them, this significantly reduces immediate pressure on domestic cell supplies.Other Important Articles Covering the same topic:Solar energy systems: What is the science behind clean energy generation?UPSC Prelims Practice Question Covering similar theme:(3) Consider the following statements:1. From June 1, 2026, only locally manufactured solar cells can be used in domestic, commercial and industrial solar projects.2. This domestic cell sourcing mandate is aimed at reducing India’s dependence on imports and strengthening the domestic solar manufacturing ecosystem.Which one of the following is correct in respect of the above statements?(a) Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation for Statement 1.(b) Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation for Statement 1.(c) Statement 1 is correct but Statement 2 is incorrect.(d) Statement 1 is incorrect but Statement 2 is correct.Must be vigilant on inflation, may face demand headwinds: Fin MinSyllabus:Preliminary Examination: Current events of national importance, Economic and Social Development.Mains Examination: General Studies-II, III: Government policies and interventions, Indian Economy and issues, transport and marketing of agricultural produce and issues and related constraints; e-technology in the aid of farmers, supply chain management.What’s the ongoing story: Consumption demand in India may face headwinds in the coming months with economic conditions beginning to show the impact of the conflict in West Asia, the Ministry of Finance said on Saturday, warning that while the near-term outlook is one of “cautious resilience”, policy will need to “remain agile across monetary, fiscal, and structural dimensions” to tackle the ongoing uncertainty and that inflation developments warrant “vigilance”. Key Points to Ponder:— What is inflation?— Know the Types of Inflation like Moderate Inflation, Galloping Inflation, Hyperinflation, Stagflation, Deflation, Core Inflation etc. — How is inflation measured in India? — What are the causes of Inflation in the present situation?— What is the difference between core and headline inflation? — What is the difference between a wholesale price index and a consumer price index? — What are the impacts of high inflation on the economy?— What is monetary policy?— What is the difference between monetary and fiscal policy?Key Takeaways:— “For India, these external pressures are beginning to transmit, selectively but perceptibly, into domestic economic conditions,” the finance ministry said in its Monthly Economic Review report for May, adding that the moderation in core sector growth and fuel consumption “signals that global headwinds are gradually finding their way into select segments of domestic activity.”— It separately said a significant rainfall deficit along with the current geopolitical conditions could translate into food inflation, weakening rural demand and aggregate growth.UPSC Issue at a Glance | Decoding India’s 3F Challenge: Fuel, Fertiliser and Foreign Exchange— According to data released on May 20, growth of India’s eight core industries – namely coal, crude oil, natural gas, refinery products, fertilisers, steel, cement, and electricity – fell to 1.2% in March and 1.7% in April. Meanwhile, the India Meteorological Department on Friday cut its monsoon forecast to 90% of the Long Period Average from 92% projected in April. The latest forecast is the lowest by IMD in the last 20 years.— The comments by the finance ministry that policy will need to be “agile” and the inflation outlook warrants vigilance come days before the Reserve Bank of India’s Monetary Policy Committee announces its interest rate decision on June 5. — In its report on Saturday, the finance ministry took note of the divergence between India’s retail and wholesale inflation in April: 3.48% and 8.3%, respectively. This wedge, it said, is a sign that upstream cost pressures are building and the passthrough to consumers may not be far behind.— After holding retail fuel prices at for over two-and-a-half months amid the surge in global rates due to the West Asia crisis, public sector oil marketing companies have raised pump prices of petrol and diesel by over Rs 7 per litre in less than two weeks.— The RBI, in early April, forecast that headline retail inflation as measured by the Consumer Price Index (CPI) may average 4.6% in 2026-27, up from less than 2% in 2025-26. However, economists from outside the central bank see CPI inflation averaging more than 5%. Central banks in Asia have already begun raising interest rates, including Indonesia by 50 bps and Sri Lanka by 100 bps – both in one go – in the last 10 days.Do You Know:— Inflation refers to the rate at which the general price level for goods and services increases over a period of time, causing a decrease in purchasing power of money or real income. In other words, as inflation rises, each unit of currency can buy fewer goods and services than before.— Rising inflation affects the financial well-being of households, especially those with lower incomes or fixed incomes. As the cost of goods and services increases, it reduces the quantity of goods and services that can be purchased with the same nominal income, thereby affecting households’ cost of living.— CPI inflation, which measures the change in consumer prices of hundreds of goods and services in a given month compared to the same month in the previous year, is the most important economic indicator in the country as it directly influences the level of interest rates set by the Reserve Bank of India (RBI). — Wholesale Price Index (WPI): While the CPI measures the price changes in the retail market (maximum retail prices{MRP}, inclusive of taxes), the WPI measures the price changes in the wholesale market. Say, for example, the price of a commodity (such as onions) would vary depending on the fact that it is bought from the wholesale market or retail market. Other Important Articles Covering the same topic:Everyday Economics: What are WPI and CPI inflation rates? Previous year UPSC Prelims Question Covering similar theme:(4) Consider the following statements: (UPSC CSE 2020)1. The weightage of food in Consumer Price Index (CPI) is higher than that in Wholesale Price Index (WPI).2. The WPI does not capture changes in the prices of services, which CPI does.3. The Reserve Bank of India has now adopted WPI as its key measure of inflation and to decide on changing the key policy rates.Which of the statements given above is/are correct?(a) 1 and 2 only(b) 2 only(c) 3 only(d) 1, 2 and 3ALSO IN NEWSGovt waives import duty on cotton till October 30The government on Saturday announced removal of 11% duty on cotton starting June 1 till October 30 to boost cotton availability for India’s textile industry amid the ongoing West Asia crisis. This is the second time in the last 12 months that the duty has been removed.A similar relief measure was extended to the industry last year after the US imposed steep tariffs on Indian exports. The Ministry of Textiles said that the temporary duty exemption is expected to reduce input costs across the textile and apparel sector, thereby providing a targeted relief to manufacturers and consumers, while also keeping the interests of domestic farmers in mind.‘Carbon rules, sustainability norms make ESG a compliance priority for industry’Frameworks such as the EU’s carbon tax and the proposed Carbon Credit Trading Scheme by India are rapidly transforming environmental, social and governance (ESG) practices from a voluntary disclosure exercise into a key business and compliance priority for industries, say experts. Without credible carbon data systems and traceable reporting mechanisms, companies could face increasing compliance risks and competitive disadvantages in global markets, they said.In travels of Buddha’s sacred relics, India’s soft power outreachThe day the Piprahwa relics landed on the small airstrip in Leh, hundreds of people gathered to catch a glimpse. Once the relics were on their way to Jivetsal, to be displayed for two weeks, Leh saw an unprecedented traffic jam that extended as far as the eye could see. This wasn’t the first time the Buddha’s relics had come to the valley, though – they had been brought to Leh for a public exhibition earlier in 1950. PRELIMS ANSWER KEY1. (b) 2. (b) 3. (a) 4. (a) Subscribe to our UPSC newsletter. Stay updated with the latest UPSC articles by joining our Telegram channel – Indian Express UPSC Hub, and follow us on Instagram and X. Click Here to read the UPSC Essentials magazine for May 2026. Share your views and suggestions in the comment box or at manas.srivastava@indianexpress.com