Complex sentence: The huge mortar could be ready to fire in 12 hours, while the largest (800 mm) known German artillery weapons were hauled on 25 railway cars and required three weeks to put in firing position.
Split into simpler sentences: The huge mortar could be ready to fire in 12 hours. The largest (800 mm) known German artillery weapons were hauled on 25 railway cars and required three weeks to put in firing position.