Prime Minister David Cameron slipped up when he described Britain as the "junior partner" of the US in fighting Nazi Germany in 1940, when America did not join the Second World War until a year later.
The US maintained neutrality until Germany and Japan declared war on it in December 1941 following the attack on Pearl Harbour, though it did supply the UK with war materials.
But Mr Cameron got his history wrong in an interview on Thursday, as he explained his view of Britain as the junior partner in the transatlantic special relationship.
"I think it's important in life to speak as it is, and the fact is that we are a very effective partner of the US, but we are the junior partner," the PM told Sky News.
"We were the junior partner in 1940 when we were fighting the Nazis."
Downing Street on Thursday insisted Mr Cameron's comments were not intended to belittle the efforts of Britain's troops at a time when the UK and its empire stood alone against the Nazis.
"The last thing that the Prime Minister would have wanted to do is create that impression," said a spokeswoman.
"He holds the armed forces in a very high regard. He was referring to the current relationship between the UK and US."
