Composer Bertus van Lier was a versatile and determined intellectual. From the start of World World II he upheld his principles against the occupier. During and after the war he maintained this attitude towards those colleagues who were suspected of collaboration with the enemy. In compositions written during the war, Van Lier expressed his resistance to the deprivation of liberty, especially in his vocal works. After the liberation his work as composer diminished and he focused on his activities as a musicologist, pedagogue and publicist.