The Trump administration’s decision to temporarily suspend the delivery of all military assistance to Ukraine sent shock waves through Europe on Tuesday, even as details about the move remained scant.
The decision — which affects more than $1 billion in arms and ammunition in the pipeline and on order — made real a fear that has racked Ukraine since Mr. Trump’s re-election.
Here’s what to know.
Why is the U.S. suspending aid?
In the run-up to Mr. Trump’s inauguration, the Biden administration rushed to deliver as much support to Ukraine as it could out of concern that Mr. Trump would cut military assistance. And President Volodymyr Zelensky of Ukraine has been working furiously to shore up European support.
Mr. Trump’s overtures toward Russia since he took office aggravated those fears — culminating with an explosive confrontation in the Oval Office on Friday between the U.S. leader and Mr. Zelensky. Mr. Trump castigated the Ukrainian president for not being grateful enough for U.S. support in the war with Russia.
The decision to suspend aid came out of meetings at the White House on Monday between Mr. Trump and his senior national security aides, according to senior administration and military officials, who spoke on the condition of anonymity to discuss internal deliberations. It appears aimed at forcing Mr. Zelensky to agree to a cease-fire on terms Mr. Trump dictates, or condemns the country to larger battlefield losses.
The officials said the directive would be in effect until Mr. Trump determined that Ukraine had demonstrated a good-faith commitment to peace negotiations with Russia. It was not immediately clear what that might look like or how long the suspension will last. For now, it will be up to Kyiv and its European allies to try to keep Ukraine’s guns firing.
Has this ever happened before?
Mr. Trump’s move has few direct precedents in recent American history. The United States has paused the transfer of specific weapons systems to allies and partners, like when President Joseph R. Biden Jr. suspended deliveries of 2,000-pound bombs to Israel that he feared could be used against civilians in Gaza. But a full cutoff is unusual, and is essentially an ultimatum.
It is not the first time Mr. Trump has blocked aid to Ukraine. During his first term, he pushed Mr. Zelensky to help tarnish Mr. Biden when he was the leading Democratic candidate for president. He withheld military aid to Ukraine at the same time — releasing it only after pressure from advisers and Republican senators. Revelations about those actions led to Mr. Trump’s first impeachment.
How much aid has Ukraine received from the U.S.?
Ukraine has depended on a lifeline of arms from the United States since the day after Russian troops crossed the border in February 2022, when the Biden administration authorized $350 million worth of arms from the Defense Department’s stockpiles for Ukraine.
The Pentagon went on to send 71 more shipments of military aid from existing stockpiles worth $33.8 billion.
The United States has also provided $33.2 billion under a program called the Ukraine Security Assistance Initiative, which provides funds that Kyiv can only use to buy new military hardware directly from U.S. defense companies.
In total, the United States has spent about $119 billion on the war in Ukraine, with $67 billion of that going to military spending, according to one frequently used tracker. Europe has dedicated about $138 billion to Ukraine, of which about $65 billion has been in military aid.
Mr. Trump has vastly overstated the amount of aid the United States has given Ukraine.
According to the Pentagon, about $3.85 billion remains of what Congress authorized for additional withdrawals from the Defense Department’s stockpile for Ukraine.
What’s at stake?
Ukraine relies on the United States for Patriot air-defense missiles, which are the only system capable of intercepting Russian ballistic missiles, such as the Kinzhal hypersonic missiles that have been fired at Kyiv.
It also has received advanced weapons, including surface-to-surface ballistic missiles, along with more than three million 155-millimeter artillery shells, tens of thousands of guided artillery rockets and antitank missiles, thousands of antiaircraft missiles and armored vehicles and dozens of tanks. The United States also provides Ukraine with parts, maintenance and technical support.
What will the impact be?
Mr. Zelensky has said that losing U.S. military assistance would be a devastating blow but that Ukrainian forces would keep fighting.
European leaders have pledged their unwavering support and further aid for Ukraine. And Ukraine’s reliance on American ammunition, howitzers and armored vehicles has lessened as its own arms production has ramped up and exploding drones, also made domestically, have surpassed other weapons in lethality.
Through its own weapons production and arms deliveries from Europe, Ukraine could withstand a U.S. shutdown for some weeks or even a few months, U.S. officials and analysts said on Monday.
“The reality is that Ukraine is far less dependent on the United States for its day-to-day combat needs than it was a year ago,” said Michael Kofman, a senior fellow at the Carnegie Endowment for International Peace, who has visited Ukraine several times since the war started three years ago.
When U.S. military aid stopped flowing last year for several months, the protection provided by Patriot air defense batteries frayed and Russian missiles pounded Ukraine’s energy infrastructure. It took longer for the impact to be felt on the front lines, where Ukrainian commanders said they were forced to ration ammunition as supplies dwindled.
Reporting was contributed by Andrew E. Kramer, Marc Santora, Erica L. Green, Eric Schmitt, David E. Sanger and Julian E. Barnes.
