The US announced on Friday that it would withdraw 5,000 soldiers from Germany, its largest European base, in the latest strain in its relations with Europe amid a rift over the Iran war and tariffs.US President Donald Trump had threatened a drawdown in forces earlier this week after German Chancellor Friedrich Merz accused Washington of entering the war in West Asia without a clear strategy. Merz said Iran was “humiliating” the US in negotiations.The US has stationed tens of thousands of troops across its European bases, using them as logistics and launch sites for its wars. A significant chunk of these troops (around 40,000) is in Germany.This forward deployment (positioning forces close to potential conflict zones) is also a key part of NATO’s defences and its deterrent against traditional foes such as Russia.Here is a look at why the US has military bases in Europe, why so many of its troops are in Germany and how Trump’s threat to wind them down may end up hurting the US — and push Europe away from NATO towards its own defence pact.The history of US troops in Germany is a direct legacy of World War II. After the Allied victory, US troops stayed back primarily as an occupation force.But as one war gave way to a different kind of conflict — the Cold War — the strategic rationale behind the troop presence evolved. Germany’s geographic positioning within Europe made the country ideal for the US to deter Soviet aggression away from home.Story continues below this adAt the height of the Cold War in 1975, US troops in Europe numbered around 3,20,000. These forces were vital to the US projection of power globally.The collapse of the Soviet Union prompted a steady drawdown of forces in subsequent years and a shift in the role played by these bases — they became vital forward-staging sites and logistical hubs for US military operations, The Guardian wrote.According to a 2021 Naval War College analysis, by 2013, the US had withdrawn its last heavy Brigade Combat Teams (BCTs) and the V-Corps headquarters from Europe.Also Read | Who are Israel’s West Bank settlers?Story continues below this adDespite these drawdowns, the US still maintained a permanent presence of around 68,000 active personnel across 20 to 40 bases in Europe as of the end of last year, according to the US Defense Manpower Data Center.More than half of these troops — around 40,000 — are stationed in Germany, according to German Defence Minister Boris Pistorius.The US presence in Germany includes the giant Ramstein airbase — the HQ for US air forces in Europe, which houses 8,500 air force personnel — and Landstuhl hospital.Both of these have been used by the US to support its war in Iran, as well as previous conflicts in Iraq and Afghanistan.How Trump has shaken up US overseas deploymentStory continues below this adThis is not the first time Trump has moved to draw down US presence abroad.On June 15, 2020, he announced his intentions to downsize American troops in the region by roughly 10,000. Within weeks of this initial announcement, then defense secretary Mark Esper expanded this figure to 12,000 troops.The plan entailed the complete withdrawal of the US Army’s 2nd Cavalry Regiment (2CR) from the European theatre, bringing 6,400 troops back to the US and relocating another 5,600 to other allies in the region such as Italy and Belgium.Pentagon officials subsequently attempted to frame the decision as a maneuver to enhance strategic flexibility. This did not offset the tremors sent out by Trump’s initial statements where he referred to Germany as “delinquents” while expressing his displeasure at its government’s failure to meet NATO’s defence spending targets — specifically the commitment to spend 2% of GDP on defence and 20% of the defence budget on equipment.Story continues below this ad US bases abroadIn February 2021, the Joe Biden administration halted and reversed the drawdown plan, keeping most US forces in place.But when Trump came back to power, he picked up right where he left off. He pressured European allies to spend more on their own defence and criticised them for relying too heavily on US protection.Now, amid wide-ranging disagreements with Europe — from Greenland and NATO to the Iran war and tariffs — Trump has decided to pull out troops from Germany. And he has threatened to do the same for troops in Italy and Spain.The US had over 12,000 troops in Italy and around 3,800 in Spain at the end of last year, shows the US Defense Manpower Data Center.Story continues below this adThese moves show that Trump’s transactional approach to the European alliance now supersedes traditional deterrence in the region.What happens once the US leaves?The Pentagon decision means one full brigade will leave Germany and a long-range fires battalion that was due to be deployed later this year will be cancelled.The loss of the long-range fires will be a particular blow to Berlin, as it had been due to form a significant extra element of deterrence against Russia while Europeans developed such long-range missiles themselves.To be clear, it could also hurt the US — not only in terms of force projection but also financially.Story continues below this adFor the 2020 plan, for instance, the Pentagon estimated that relocating 12,000 troops would cost $6-8 billion. This was 21 times greater than the US European Command’s entire 2020 military construction budget.Also Read | ‘Ecocide’: How international law falls short in addressing the environmental toll of warThe specifics of the latest plan are not clear yet, but it is clear that it will not be cheap.The US Army doctrine does not contain the word retreat, using the term “retrograde operation” instead. A complete withdrawal of major ground units is, in doctrinal terms, a retrograde operation that will do little to allay Europeans fears of a Russian threat.Story continues below this adNATO members have pledged to take on more responsibility for their own defence but with tight budgets and vast gaps in military capability it will take years for the region to meet its own security needs.So what can Europe do?The planned drawdown of U.S. troops from Germany should spur Europeans to strengthen their own defences further, German Defence Minister Pistorius said on Saturday.“We Europeans must take on more responsibility for our own security,” Pistorius said. He said: “Germany is on the right track” by expanding its armed forces, speeding up military procurement and building infrastructure.Germany wants to boost the number of active-duty Bundeswehr soldiers from a current 185,000 to 260,000, though critics of the defence minister have called for more in response to the widely perceived threat from Russia.But it’s not just Germany.Faced with mounting doubts over NATO’s reliability and with states such as Spain openly criticising Trump’s expectations, the EU is preparing a possible mutual assistance pact.This would mark a pivot from NATO’s Article 5, which says an attack on one member is considered an attack on all members and requires a collective response.This is a turn, instead, towards Article 42.7 (introduced via the Lisbon treaty) of the Treaty on European Union (TEU) to offer Europe NATO-like collective defence.NewsletterFollow our daily newsletter so you never miss anything important. On Wednesday, we answer readers' questions.SubscribeA look at both texts shows the EU’s clause is a few degrees stricter than Article 5.NATO’s Article 5 requires allies to take “such action as it deems necessary”. This leaves room for variable (and non-combative) responses.In contrast, Article 42.7 states that if a member state is the victim of armed aggression, the other member states have “an obligation of aid and assistance by all the means in their power”.The catch here lies in the military reality of the two texts. NATO’s deterrence is rooted in an integrated military command structure, decades of joint interoperability exercises, and the sheer magnitude of the US logistical footprint. The EU currently lacks a unified military command structure to orchestrate a large-scale territorial defence.Further, Article 42.7 contains a specific legal carve-out to protect the constitutional neutrality of EU members such as Austria and Ireland (who refused to sign without ensured neutrality).The caveat reads that when assisting another member state, actions undertaken “shall not prejudice the specific character of the security and defence policy of certain Member States”.So, this essentially acknowledges that the EU is not a monolithic military alliance.