U.S. President Joe Biden has ruled out sending U.S. troops to fight in Ukraine, but American-made weapons are already there in force, and more will be on the way. How effective they would be in turning back a Russian invasion is another question.

Since 2014, the United States has committed more than $2.7 billion in security assistance to Ukraine, according to the Pentagon, including a $200 million package in December comprising equipment such as Javelin anti-tank missiles and other anti-armor systems, grenade launchers, large quantities of artillery, mortars and small-arms ammunition.

But military experts say that with 150,000 troops on three sides of Ukraine, the Russian army could quickly overwhelm the Ukrainian military, even one that is backed by the United States and its European allies. Ukrainian forces stretched thin by defending multiple borders would have to prioritize which units received advanced weaponry and extra ammunition.