During World War I, Bastin fought as in lieutenant in the Belgian 1er régiment de Chasseurs à cheval.
At the beginning of World War II, he held the rank of colonel and served as Chief of Staff of the Belgian Cavalry Corps.
After the invasion of Belgium by the Germans in 1940 he fled to France and joined the underground movement by taking command of the Belgian Legion.
The Belgian government based in London made him the commander of all their underground military forces on 30 December 1942.
The Belgian government promoted him to the rank of major general posthumously in August 1946.