Secret Map of the Battle of Balikpapan

Seventy years ago the Battle of Balikpapan (July 1-21, 1945) was ongoing. This was the concluding stage of the Borneo campaign that removed the Japanese from the island and one of the last battles of World War II. It was mostly fought by Australian troops, but there were also US troops involved, including my wife's Uncle. He gave me some maps and diagrams from the war, including this remarkably detailed map.

Hopefully by now it is safe to show details of a secret map.

This Dutch topographic map was annotated by the Australian Army Topo Survey. The annotations (in red) show enemy positions, trenches, tunnel entrances, bunkers, landing obstacles and observation towers.

The legend shows the range of details that were annotated

Balikpapan was and still is an important oil producing center. Destroyed oil tanks are X-ed out in red.

Folded into the map was an invasion diagram for Green Beach. His name (Lt. Garfinkle) appears twice - on the second wave and also in the bottom right corner (I'm not sure what that area of the diagram means.)

Green Beach was annotated over the map. I suspect it was only given that name for the purpose of this invasion. There is also mention of a "yellow beach" though it is not shown on the map.

 The area was heavily booby-trapped with mines and submerged logs tied together with wires. Landing craft could only approach after heavy aerial bombardment and mine sweeping. The LVT's mentioned on the diagram are amphibious tanks.

There is a very detailed description of the battle on Digger History, an unofficial history of the Australian and New Zealand Armed Services. Most of the places mentioned on the first part of that page can be found on the map so it's been interesting to read it with the map open.

After the beach and highway were secured the troops needed to disable antiaircraft positions and capture the nearby ridge so that Japanese snipers would no longer have a high place to shoot from. Hill 87 at the bottom of the ridge was a fortress of trenches and tunnels.

When this area was finally secured, they moved on to capture Newcastle (Hill 99 on the right edge of the map below.) This high area overlooks the town and harbor of Balikpapan and was a good location to launch an attack on the town. 

I did not get a chance to talk to my Uncle-in-law about his role in this battle while he was still alive so unfortunately all I know is from his placements on the diagram.