Very few Invasions have failed, because the attacker assembles such a force and chooses a time & place which "guarantees" the success of the landing.

Preventing a breakout however is different.

The Normandy breakout could have been much harder id the 15th Armee was released from the Pas de Calais earlier and had time to set up stronger defenses around the beachhead.

But they would still have to battle against the overwhelming Allied Air Supremacy over France.

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Whe're off to see the Wizard, the wonderful wizard of OZ - 6 Australian Infantry Div, Bardia January 1941