He was the only son of Manuel Caetano da Silva (1870-1926) and wife Maria da Encarnação Vassalo (1869-1922) and brother of Maria da Conceição, married with issue, Joana and Aurora.
When the Republic of India sought to annex the territories of Goa, Daman (from which had been previously separated in 1954 and annexed by India in 1961 the enclave of Dadra and Nagar Haveli) and Diu from Portuguese control in December 1961, Manuel Vassalo e Silva, recognizing the futility of facing a superior enemy, disobeyed direct orders from the Portuguese President of the Council of Ministers António Salazar to fight to the death and offered to surrender without a fight. After that he fell into disgrace at the eyes of Salazar, who never accepted the consumated fact of the anexation.
Recently it was said by the Goan-Portuguese politician Narana Coissoró that Salazar sent him a cyanide capsule for the case of being defeated.
Family
He was married to Fernanda Pereira e Silva Monteiro and had issue, a son and two daughters:
Fernando Manuel Pereira Monteiro Vassalo e Silva (Lisbon, December 6, 1925 – Lisbon, June 9, 2006), married to Maria Amélia Franco Veiga (Lisbon, March 20, 1932 – March 17, 2004), daughter of António Veiga and wife Rosa Maria Garcia Franco, and had issue, seven children, two married and had issue
Maria Fernanda Pereira Monteiro Vassalo e Silva, married to Rui António da Cunha Bernardino, and had issue, eight children, six married and had issue
Maria da Luz Pereira Monteiro Vassalo e Silva, married to António Faias Sors Lagrifa, born in Luanda, and had issue (their son Jorge Manuel Vassalo Sors Lagrifa (May 7, 1948 – February 6, 2005) was the second husband without issue of Ana Cristina da Gama Caeiro da Mota Veiga, born in Lisbon, Santos o Velho, on June 4, 1950, daughter of António da Mota Veiga and wife Maria Emília da Gama Caeiro, formerly married and divroced from Marcelo Rebelo de Sousa)
