While the German Navy and the Island Nation Navy fought a decisive battle in the Pacific Ocean, the German Army's offensive against the Indonesian archipelago was likewise in full swing.
On Sumatra Island, the German 11th Army Corps captured Medan, and the 7th Area Army of the Island Nation's Army was completely annihilated under the German military's Encirclement Offensive. General Seishiro Itagaki and dozens of generals beneath him all committed seppuku.
Afterward, the German 11th Army Corps, 3rd Army Corps, and 13th Army Corps advanced southeast along the Malacca Strait, fighting the 14th Area Army of the Island Nation's Army, the 2nd Army, and the 18th Army.
Although the 14th Area Army of the Island Nation's Army possessed formidable strength, and both the 2nd Army and the 18th Army had several divisions, they clearly could not hold out on Sumatra Island against the main forces of the German military's three army corps. They were defeated again and again.
On Java Island, after dealing with the 5th Area Army of the Island Nation's Army, the German 12th Army Corps, 4th Army Corps, and 16th Army Corps crushed the 4th Army and 38th Army of the Island Nation's Army, squeezing all its remaining forces on Java Island into the Batavia line.
Although the 18th Area Army of the Island Nation's Army still had some troops, it was virtually impossible for it to withstand the fierce offensive of the German military's three army corps.
On New Guinea Island, the 10th Area Army and the 31st Army of the Island Nation's Army likewise retreated step by step under the attacks of the German 22nd Army Corps and 24th Army Corps. Quite a few Island Nation soldiers were scattered and fled into the dense primeval forests.
At that time, the South Seas remained largely undeveloped.