In the army, he distinguished himself as a polyglot with full understanding of many local and regional languages and dialects. His linguistic skills were very useful for the military and were always in high demand. He moved around Portuguese Guinea, which was being subjected to an intense guerrilla war instigated by foreign countries, integrated in many missions and operations and working on this capacity. Soon he would start to have a full understanding of the tactical aspects of guerrilla war and counterinsurgency operations and would master them. So he enrolled in special operations training courses and graduated as a commando. In the following years, Marcelino da Mata became known for his many acts of bravery and heroism during the Portuguese Colonial War. Having participated in 2412 command operations, he is the most decorated Portuguese military officer in the history of the Portuguese Army. Demobilized by the departing Portuguese military authorities after the Carnation Revolution of 1974 in Lisbon and the independence of Portuguese Guinea has been agreed, a total of 7,447 black Guinea-Bissauan African soldiers who had served in Portuguese native commando forces and militia were summarily executed by the PAIGC after the independence of the new African country. He managed to escape the same tragic fate of other black Portuguese soldiers in Guinea-Bissau because he was in mainland Portugal in order to receive medical care due to a wound caused by a firearm accidentally shot by another Portuguese soldier shortly after the Carnation Revolution (which effectively ended the war) has taken place in Greater Lisbon, a Portuguese region where he would live the rest of his entire life. Not without being tortured by the Portuguese far-left in 1975 during a tumultuous revolutionary period called "Processo Revolucionário em Curso" (PREC).