Thank you for your thoughtful reply. The US empire became entangled in Vietnam during the 1950s following the French defeat and withdrawal from the country in the mid 50s. As the US massively escalated its military presence in Vietnam during the late 60s its key architects in the Johnson government believed that overwhelming firepower would defeat a poor 'backward' country such as North Vietnam. The Pentagon became obsessed with the numbers of Vietcong it killed each day. Of course, the US empire approach failed totally to overcome the socio economic realities on the ground. The peasantry of South Vietnam wanted an end to the terrible exploitation/misery of landlordism and supported the revolutionary forces whose programme of land redistribution and an end to the myriad of evils of landlordism was the granite foundation of their support for the Vietcong. No amount of murder/violence//firepower by US forces could overcome this burning desire of the peasantry to be free.
I would recommend the history of the conflict by Gabriel Kolko Anatomy of a War.