Also on Italy, in the original timeline, it seems to me that it helped to underscore just how far up the creek without a paddle the Western Allies could end up, if and when the Germans responded in strength and with speed to a landing. The way the British were blocked on Sicily until Patton came around the flank, the near debacle at Salerno, and the Anzio siege all emphasised that the Western Allies were going to have to be prepared for some hard grinding fighting in Normandy (although it might have been less severe if they'd anticipated the bocage
...)
Strictly on the question of Italy.
It turns out that operations to reach the Gustav Line took about 2 months though to reach the Volturno was just an incredible 30 days.
Just HOW MASSIVE the Invasion of Italy is can be read here.
How it developed can be seen by this map
.
There is some controversy about Montgomery's rate of advance. Depending on whose sources, Montgomery either was delayed by the terrain, enemy engineer demolitions and road-net or he completely duffed up and sat on his army organizing a push at Calabria for a whole critical day and let the whole plan of sucking the Germans into a hammer and anvil attack and hook envelopment go right out of possibility.
It is true that he sat on his organizational imperatives for a whole day at Calabria where Patton would have pushed forward regardless of the chaos, casualties and risks.
It is also true that the Germans and their fascist Italian allies blew bridges and bottlenecked every road chokepoint with delay parties that they could and this slowed the Baytown advance up.
The Texans started hating Mark Clark's guts by 17 September 1943. It turns out the 36th US Infantry had to Alamo at Salerno. For some incredibly stupid reason, the Germans thought the Americans would be pushovers.
Anyway they, the Germans, were wrong and Foggia was in hand and could be sustainable by NLT 1 December 1943. While
@Athelstane and I have gone back and forth on Anzio, there is no doubt that Baytown and Avalanche did exactly what the operations needed to do. Now using the advantage gained is an airpower matter and exceeds the scope of this topic.
