U.K. Prime Minister Keir Starmer has made public what has been known privately for a while now: The United Kingdom will deploy troops as part of a non-NATO peacekeeping force designed to preserve any U.S.-negotiated end to the war in Ukraine. His announcement is welcome but carries numerous complications.
First, there is glaring opposition from Russia. Meeting with Secretary of State Marco Rubio in Saudi Arabia on Tuesday, Russian foreign minister Sergey Lavrov said any deployment of Western troops to Ukraine would be "completely unacceptable." As the Washington Examiner has written in the past, this Russian opposition to Western peacekeepers underlines why President Donald Trump will have to stare down Russian President Vladimir Putin if he is to secure a meaningful peace accord on Ukraine.
Trump has ruled out sending U.S. troops as part of any peacekeeping force, but without European forces to defend a demilitarized zone against future Russian attack, Putin or the next dictator would be able to use any peace deal and associated sanctions relief to reconstitute forces, rebuild the Russian economy, and invent a reason to invade Ukraine again.
Ukraine will not accept a deal that does not include Western peacekeeping forces. It couldn't risk doing so. If Western peacekeepers are removed from the equation, Ukraine will keep fighting in the hope of continued European support if no longer U.S. support. Kyiv knows that a deal without Western peacekeepers would be a fake deal. It would be a breather for Russia before renewed invasion. Ukrainians will not trust rhetoric alone on Western security guarantees.
In 1994, Ukraine gave up its nuclear weapons in return for assurances from the United States, the U.K., and Russia that its territorial integrity and political sovereignty would be respected in perpetuity. That promise was broken within 30 years. Trump must make Russia understand that peacekeepers are a prerequisite for agreement. If Putin refuses to yield, Trump must follow through on his threat to cripple the Russian economy with sanctions and force Putin to negotiate in good faith.
The second challenge facing a peacekeeping operation is that of military capability.
Any peacekeeping force in postwar Ukraine must expect to face an increasingly large, well-armed, and combat-experienced Russian army that outmatches it in scale and battlefield capability. That is difficult for the U.K. to contend with. Starmer's Labour government abandoned the predecessor Conservative government's pledge to spend at least 2.5% of GDP on defense by 2030. Even that sum would have been woefully inadequate to meet the U.K.'s defense requirements.
Starmer says that he will sketch a path toward spending 2.5% of GDP on defense after examining a strategic defense review, which is expected soon. But the U.K. economy is stagnant, and public finances are strained by big increases in both domestic spending and taxes. Starmer will doubtless want to limit defense increases to pay for more welfare giveaways. It is probable that his offer to deploy British troops to support Ukraine peacekeeping is partly motivated by the hope that doing so will earn Trump's gratitude. And as an extension, Trump's willingness to give the U.K. a pass for its plan to woo China and will soften Trump's demand that allies increase defense spending to more than 3% of GDP.
The problem for the U.K. isn't simply or predominantly financial. Other European and international allies might provide money for a peacekeeping force, for example. The problem is that any peacekeeping deployment would stretch Britain's military capabilities.
As first reported by the Washington Examiner, U.K. Special Forces have guided Ukrainian counterparts in wreaking havoc behind Russian lines since the start of Russia's 2022 invasion. But military advisory support at the front is very different from mass deployment at the front. The U.K. armed forces have both been starved of resources for decades and made monstrously expensive but ineffective defense purchases. This means the British army now numbers fewer than 75,000 regular troops. The Royal Marines have fewer than 6,000 personnel.
The U.K. would struggle to maintain even 15,000 troops in Ukraine on a standard British army six-month rotation deployment structure. The British army has some units that are well suited to a flexible, combat-ready peacekeeping role in Ukraine. The problem is how many units can be maintained there over a period of years.
Balancing limited personnel numbers and budgets, the head of the British army, Gen. Roland Walker, has outlined a strategy of "velocity" centered on aggressive forward reconnaissance. While this strategy would maximize the British army's effectiveness in complementing a NATO war against Russia, it would bring challenges to a Ukraine peacekeeping deployment.
It would mean British defense against renewed Russian attack on Ukraine would depend on delaying Russian advances rather than meeting and defeating Russian forces en masse. The reality of this force structure and strategy is that the U.K. would need substantial allied support to make any peacekeeping force an effective deterrent trip-wire. And this does not take into account air power, intelligence, logistics, and other supporting components that any peacekeeping force needs.
That leads us to a third problem facing Starmer's peacekeeping pledge: Which other nations will support it and how?
It is probable that France would be the U.K.'s main ground force partner in Ukraine. President Emmanuel Macron has made clear that he views the preservation of Ukraine's democratic sovereignty as necessary for Europe's long-term security. But while he has recently increased defense spending, the hikes are nowhere near enough for prolonged peacekeeping in Ukraine. Like the U.K., France could probably just about sustain 15,000 troops from highly capable units in Ukraine. But this would require defense spending increases for years.
Because any peacekeeping force would need to be at least 50,000 strong even if it had only a trip-wire capacity, other European militaries would have to send troops to Ukraine to supplement the British and the French. Unfortunately, feckless allies such as Germany under Chancellor Olaf Scholz have already effectively ruled out troop deployments. Scholz, who spent last week whining about Vice President JD Vance's speech assailing European censorship, says it is "slightly irritating" to talk about peacekeeping. Italian Prime Minister Giorgia Meloni echoed this on Tuesday.
Fortunately, there are more courageous European powers such as the Baltic states, the Netherlands, Denmark (Trump's aggression over Greenland has not helped Danish involvement), Finland, Norway, and Sweden. Together, these nations might be able to pull together sufficient forces to make a peacekeeping force credible. At the same time, Poland, which has ruled out contributing to a peacekeeping force, should be expected to use its military strength to reinforce NATO's Baltic eastern flank. This would allow for the maintenance of NATO's defense while allowing for the diversion of European forces to support the peacekeeping mission.
All that said, however, the U.S. military will also have to play a role in any peacekeeping force even if not directly with ground forces. As Starmer has correctly pointed out, the U.S. will need to provide a "backstop" to educate the Kremlin that any attack on European peacekeepers will lead to U.S. military support for those peacekeepers. Absent that backstop, Russia will be tempted to test the peacekeeping force along the edges, if not directly. Absent that backstop, the trans-Atlantic alliance will degrade precipitously, leading to increasing European alignment with China against U.S. interests.
The imperative of a U.S. military refocus toward China means that this backstop won't be able to rely upon saturated U.S. air force deployments in Europe. Still, if Russia knows that a mass attack on peacekeeping forces will lead to U.S. airstrikes and U.S. Army armored brigades reinforcing the borders of allied states, it is highly unlikely to risk that proposition. Again, this is why Putin is so concerned with avoiding Western peacekeeping deployments to Ukraine in the first place. And again, why those deployments are the critical ingredient of a lasting peace.
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Trump's ambition to secure peace from the rubble of the worst war in Europe since 1945 is a moral one. But without peacekeeping assurance, peace will not prevail. Thus, where Trump must ensure Europeans know they will have American rear guard support for any peacekeeping deployment, European leaders must invest the funds and forces necessary to end this war for good.
Those European governments that refuse to help? They should face public ignominy and policy isolation across the board. Germany, for example, should say goodbye to every U.S. military base on its soil.