In early 1944 the Allies bombed a 1,400-year-old abbey to dust, killed no German soldiers, and handed the enemy an impenetrable rubble fortress. This episode walks through the geography that made the Gustav Line so deadly: the Apennines funnelling the advance into the Liri Valley, the flooded Rapido and Gari rivers, and German observers on the heights. It covers the US 36th Division's disastrous night river crossing that cost 2,100 men in 48 hours, the French Expeditionary Corps and its Moroccan mountain troops nearly unhinging the line before supplies ran out, and the 34th Division fighting on bare limestone to within 400 yards of the abbey at 80 percent casualties.

We then examine the controversy over whether Germans occupied the monastery, the Vatican agreement they honoured, General Tuker's discovery of 10-foot-thick walls, and the Febr ...