Four investigations Democrats could launch if they win Congress

Some experts believe that the negative publicity that would come from congressional hearings could ultimately lead to Hegseth being fired or resigning from the position.

"[If] it looks bad for the White House, and it's a drag on their media attention, President Trump might be likely to cut loose those officials, because he doesn't want that bad press," said David Miller, a political science professor and expert on the presidency at American University in Washington DC. "In a sense that could be a win for the Democrats."

Richard Painter, the former chief White House ethics lawyer under George W Bush, told the BBC that the decision to launch the war should come under scrutiny.