Tonkin Gulf Incident - A group of whales were mistaken for North Vietnamese ships which caused the US to start planning attacks. This also caused the US to up its military. The resolution ended up giving LBJ a "blank check.
On 2 August three North Vietnamese PT boats attacked the destroyer USS Maddox in international waters, in the Gulf of Tonkin. This oil painting by Commander E. Fitzgerald, January 1965 depicts the engagement.