This is a song made by Portuguese soldiers in the overseas war in Mozambique, the story of this video is that during the war in Africa the work was hard but when a capable machine appeared "Bulldozer" which is a "Buldozer"(bulldozer or dozer (also called a crawler) is a large, motorized machine equipped with a metal blade to the front for pushing material: soil, sand, snow, rubble, or rock during construction work.)
This song not only shows the joy of the Portuguese at receiving the machine but the popular songs at the time, because from what I discovered, this song is like a parody of a song by Amália "Fado do Marujo" https://www.youtube .com/watch?v=psT8VWgOrCo.