The report examined $1.699 billion in weapons sent to Ukraine that are subject to enhanced end-use monitoring (EEUM), which includes Javelin anti-tank missiles, Stinger anti-aircraft missiles, night vision goggles, AIM-9X air-to-air missiles, Advanced Medium-Range Air-to-Air Missiles, and other types of weaponry.

The IG report found that the majority of the EEUM arms, nearly 40,000 weapons in total worth approximately $1.005 billion, have not been accounted for after being sent into Ukraine.

Smaller, more portable weapons are subject to EEUM since they're more likely to be smuggled and sold on the black market.

Robert P. Storch, the Pentagon's inspector general, said there's "no record" of inventories being taken. "It doesn't mean they're not there, or they're not being used," he said, according to The New York Times.

"[But] because of their sensitivity, their vulnerability to diversion, or misuse, or the consequences of that, it's particularly important to have this additional tracking and accountability in place."

Interestingly, US defense officials have admitted significant allegations of "criminal conduct" related to US defense aid to Ukraine, according to CNN:

While delinquency could suggest weapons had been stolen or diverted away from Ukrainian forces, the inspector general said it was outside the scope of its probe to determine what had happened to the weapons that were not properly tracked.