Despite little in-game information, it is believed that the 596th Unit was the ground unit tasked with defense of the island from potential ground invasions.
Main article: Circum-Pacific War
The only known deployments of the 596th Unit occurred during the Circum-Pacific War in 2010.
On September 27, as part of Yuktobania's multi-stage attack—which coincided with its declaration of war on Osea—the Yuktobanian Air Force initiated a bombing raid on Sand Island. While Wardog Squadron dealt with the bombers and their escorts, the 596th Unit supposedly assisted in putting out fires and relocating ammunition to prevent extensive damage to the base.
The next and largest deployment of the 596th was during Operation Vanguard, the Osean defense effort against Yuktobania's attempted invasion of Sand Island on October 4. Wardog Squadron and a group of new recruits from Heierlark Air Force Base destroyed as many vessels as possible, but amphibious units managed to slip past and land on the island, resulting in a bloody ground conflict. However, the 596th prevented the capture of Sand Island after Wardog sank the Scinfaxi, forcing the remaining Yuktobanian units into retreat.
The final known deployment of the 596th occurred on December 7 during Wardog's escape from Sand Island. Soldiers of the 596th were deployed to arrest (and shoot if necessary) the members of Wardog Squadron along with Peter N. Beagle on suspicion of treason.