The city was nestled in a bay and the strait was protected from entry. The enemy, approaching by ship, had to land on the peninsula. The men of the city went to set up defenses along the hill at the narrowest point of the isthmus, preventing the enemy from approaching the city unmolested. They hastily built fences and dug trenches along the leading face of the hill.
Late that night, one of the men went back to his home to acquire some meat and bread to help sustain himself and a few of his companions for the upcoming battle. Awakened by his entry, his wife met him as he was leaving.
"We cannot fight if we are hungry. I will come back when the fight is over," he reassured her.
"For that, you have my gratitude," she responded. "Take care you return safely."
Without all, "for that" is a simple prepositional phrase. In the sentence above, it can easily be moved to the end of the sentence and still sound passable. "You have my gratitude for that."
The man returned to the trenches about an hour before dawn. The men finished making their preparations, fortifying their positions. For all that, dawn broke to find them on the wrong hill, easily surrounded or circumvented.
With all, the emphasis implies a contradiction. The phrase no longer sounds passable at the end of the sentence, probably because the connection to the antecedent of "that" would get lost.