The US Department of Defence (DoD) has been defrauding the federal government for decades. Over £16 trillion in Pentagon financial transactions between 1998 and 2015 cannot be documented or traced.
The DoD submits its annual budget request to Congress each year. As part of this it sends the previous year’s financial reports.
These account for all of the previous year’s budget even if it hasn’t been spent. Surpluses were instead siphoned off to other branches of the department.
The accountants drafted in to audit the department said there were so many mistakes and missing documents an audit was impossible.
It is hugely unlikely that no one in government knew anything about such massive fraud. Far more likely they turned a blind eye for the sake of US imperialism, based on a bloated military shoring up an economy in relative decline.