"Operation Rolling Thunder" was the codename given to the United States' strategy or action of using massive bombs during the Vietnam war in 1965.
It was a significant change in American strategy in the war because it increased military pressure on North Vietnam's communist leaders, affecting their military capacity to continue fighting against South Vietnam, whom the United States supports.
It was recorded that the United States used about 643,000 bombs, and the financial cost of the bomb effect to North Vietnam is about 300 million dollars.
