Early in the war, the US relied on a strategy of attrition, which involved inflicting heavy casualties on the enemy in order to wear them down. This strategy was not very successful, as the North Vietnamese were able to replace their losses and continue fighting.
In the late 1960s, the US began to change their tactics and adopt a strategy of pacification, which involved winning the hearts and minds of the South Vietnamese people. This strategy was more successful, and the US was able to make some progress in pacifying the countryside.
However, the US still faced a number of challenges in Vietnam, including the difficulty of fighting a war in a dense jungle environment, the lack of support from the South Vietnamese government, and the growing anti-war movement in the United States. Ultimately, the US was not able to achieve its goals in Vietnam and withdrew its forces in 1973.