The Battle of Hellzapoppin Ridge and Hill 600A consisted of a series of engagements fought in mid-December 1943 on Bougainville between forces of the United States Marine Corps and the Imperial Japanese Army.

In early November 1943, the 3rd Marine Division, under Major General Allen H. Turnage, landed at Cape Torokina near Empress Augusta Bay on the western coast of Bougainville.

[1] The landing took place as part of Allied efforts to advance towards the main Japanese base around Rabaul, the isolation and reduction of which was a key objective of Operation Cartwheel.

[4] Throughout November, the Japanese had begun moving artillery pieces into position around the perimeter and began shelling the beachhead from several hills to the east of the Numa–Numa and East–West Trails, along the Torokina River.

[5][6] Following the fighting around Piva Forks in late November, plans were drawn up by US commanders to advance towards the Torokina River where a series of high features offered significant defensive advantages that could be exploited in the event of a Japanese counterattack, which US intelligence expected.

[9] Two days later, Marines from the 3rd Parachute Battalion met resistance along a spur to the west of Eagle Creek, at a position north of the junction of the East–West Trail near Hill 1000, which later became known to US troops as "Hellzapoppin Ridge" (from the musical) because of its difficult terrain,[9] part of a feature the Japanese dubbed "Picha Mountain".

[9] The hill threatened the flank of the 3rd Parachute Battalion's position, and as a result the Marine commander was forced to readjust his dispositions to place the spur to his front.

Conversely, despite having captured a Japanese map which detailed their positions, lack of familiarity with the terrain and the confined nature of the approaches to it adversely affected the tactical thinking of the US company commanders.

[12] Prior to the attack, a thorough artillery preparation was followed by a fourth airstrike, which was undertaken by six Grumman TBF Avengers from VMTB-143, that through close coordination by forward observers on the ground, dropped forty-eight 100-pound (45 kg) bombs about 75 yards (69 m) in front of the US positions.

These lasted for three days and penetrated far behind the Japanese lines, but they did not prove fruitful for the Marines, resulting in no contact to offset the hardships faced in coming to grips with the terrain.

[13] Japanese activity during this time was limited to artillery barrages that were brought down largely on the US supply dumps that were located to the southwest around Evansville and which, as a consequence, resulted in only a few casualties.

[15] Upon receipt of the report, Turnage decided to establish a platoon-sized outpost on the hill, and on 22 December a force from the 3rd Battalion, 21st Marines, which included heavy weapons support and an artillery forward observer, was sent out to occupy it.

[15] Company I was sent up, and its commander, misreading the situation and thinking that the Japanese held the crest of the ridge rather than the foot of its reverse slope, ordered a three-pronged "double envelopment" maneuver,[15] utilizing two elements of his force to flank while the third attacked frontally.

Consequently, they too began to take heavy fire, and as a result Company I commander gave the order to withdraw so that an artillery strike could be called down on the Japanese.