Apparently this footage is from the Chinese side.

Also know as the 3rd Indochina war after ,starting with the Sino Soviet split the CCP was getting concerned over the growing Soviet power in the new "glorious revolution" in Vietnam.
basically there was a long line of events that led to China wanting to invade Vietnam in 1979...The Vietnamese had invaded Cambodia (now Kampuchea) in an attempt to oust the murderous Khmer Rouge government. The Chinese disapproved and invaded in 1979 as a punitive measure.

A PRC force of 200,000 men supported by armor many who were advisors just recently in the war against the Americans invaded.

The Vietnamese put up thier own force of 100,000 militia and 60,000 regulars but keeping thier main army in the rear by Hanoi.The red Chinese got about 20 kilometers in Vietnam when thier human wave/meat grinder theory got bogged down in Cao Bang,Lao Chi and Lang Son.In the couse of 1 month the red Chinese lose over 26,000 men kia but that number is unknown some say more some say less.Vietnam lose around 20,000.

The PRC threw everything they had as you can se on the clip they used chemical weapons(the gas masks) and a scorched earth policy.The Vietnam army used guerilla warfare and even some left over US equipment.The PRC eventually withdrew.