For most soldiers in the Vietnam-era, the time between getting drafted or volunteering and their heading to war was short. The Army had each draftee for only two years. After they were shipped to basic, trained, shipped overseas, plus the time needed to ship home and use their two months of accrued leave, each draftee could expect a year of deployed time preceded by 4-6 months of training.
Volunteers, especially officers, had it a little better. They may train for up to a year before deploying — attending advanced training like Ranger School after basic and job training.
Either way, they were expected to grow from boys to men quickly. For the three men in this video, that growth would be harder than most. The veterans fought at the Battle of Dak To, one of the bloodiest American battles of the war. Hill 875, the single costliest terrain feature of the war, was captured there.