I’ll be nice.
“We can be sure that the angry meaning of pissed off became popular among the Armed Forces in World War II, and entered into mainstream use during the post-war years. In 1946 it was defined as a new word in American Speech XXI: "This means roughly, fed-up, irritated, depressed." Some linguists and historians think the expression must have been well known during the war years, citing a story about General Eisenhower's dog. The story goes that the dog (Felix) urinated on a map and the officers joked that the enemy was "pissed off." (Leonard Mosely, Marshall, 1982).”