Complex sentence: However, German forces refused to relinquish their control of the city, which had been converted into a fortress, and the garrison there was "masked" by Allied troops, notably 1st Czechoslovak Armoured Brigade.
Split into simpler sentences: However, German forces refused to relinquish their control of the city, which had been converted into a fortress. The German garrison there was "masked" by Allied troops, notably 1st Czechoslovak Armoured Brigade.