About 300 yards (270 m) long and consisting of sheer sides that rose to a sharp crest no more than 40 yards (37 m) wide, the spur was heavily vegetated and provided many advantages to defending force.
Offering good concealment, this made accurate target identification difficult and reduced the effectiveness of the Marines' air support as well as the indirect fires offered by their artillery and naval gunfire support.
The Japanese defenders were well dug-in on the position, occupying the reverse slope, and having established a series of mutually-supporting positions that were protected with overhead cover and were supported by snipers who were tied-in to the tree tops.
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, who were unable to concentrate their forces beyond platoon strength in the thick jungle and which consequently took away from them one of their main advantages, firepower.

Commencing on 12 December, a series of assaults were attempted by the 21st Marines, utilizing the "partial envelopment" tactic.
The well-sited Japanese positions, however, turned any attempt to take the position by an indirect approach into a frontal assault.
Although the Japanese fields of fire were limited by the narrowness of the position, they were well concealed and as a result, at least initially, the first that the Marines knew of the location of the Japanese positions was when they were engaged by them at close range.

Attempts to reduce the Japanese positions through the use of mortars, artillery and airstrikes were hampered by the dense jungle – the thick vegetation caused tree bursts, while reducing the observation of attacking pilots which resulted in inaccurate strafing and bombing – and as a result it was not until 18 December that a large-scale attack could be launched by the Marines to take the hill.
That morning three airstrikes were undertaken, along with an artillery barrage, in preparation for an attack at nightfall.

Prior to the attack, a thorough artillery preparation was followed by a fourth airstrike, which was undertaken by six Grumman TBF Avengers from VMTB-134, 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.
The aircraft also conducted strafing runs of the Japanese positions.
A two-pronged attack was then put in by the 1st and 3rd Battalions, 21st Marines.
Companies 'A' and 'C' from the 1st Battalion attacked the position from the northwest, while Companies 'L' and 'K' from the 3rd Battalion attacked from the south.
This proved successful as the defenders had been forced from their dug-outs by the earlier artillery fire and air strikes, making them easier targets for the Marines.
The previous strikes had also had the effect of clearing some of the vegetation, which made the going easier for the Marines during the attack.

In capturing Hellzapoppin Ridge, the Marines lost 12 men killed and 23 wounded.
Japanese losses were at least 50 killed.
The morning after the attack, the 1st Battalion, 21st Marines exploited the position as far east as the Eagle River – which flowed into the Torokina – where they began work on constructing defensive works to consolidate their position.
About 300 yards (270 m) long and consisting of sheer sides that rose to a sharp crest no more than 40 yards (37 m) wide, the spur was heavily vegetated and provided many advantages to defending force. Offering good concealment, this made accurate target identification difficult and reduced the effectiveness of the Marines' air support as well as the indirect fires offered by their artillery and naval gunfire support. The Japanese defenders were well dug-in on the position, occupying the reverse slope, and having established a series of mutually-supporting positions that were protected with overhead cover and were supported by snipers who were tied-in to the tree tops. 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, who were unable to concentrate their forces beyond platoon strength in the thick jungle and which consequently took away from them one of their main advantages, firepower.
Commencing on 12 December, a series of assaults were attempted by the 21st Marines, utilizing the "partial envelopment" tactic. The well-sited Japanese positions, however, turned any attempt to take the position by an indirect approach into a frontal assault. Although the Japanese fields of fire were limited by the narrowness of the position, they were well concealed and as a result, at least initially, the first that the Marines knew of the location of the Japanese positions was when they were engaged by them at close range.
Attempts to reduce the Japanese positions through the use of mortars, artillery and airstrikes were hampered by the dense jungle – the thick vegetation caused tree bursts, while reducing the observation of attacking pilots which resulted in inaccurate strafing and bombing – and as a result it was not until 18 December that a large-scale attack could be launched by the Marines to take the hill. That morning three airstrikes were undertaken, along with an artillery barrage, in preparation for an attack at nightfall.
Prior to the attack, a thorough artillery preparation was followed by a fourth airstrike, which was undertaken by six Grumman TBF Avengers from VMTB-134, 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. The aircraft also conducted strafing runs of the Japanese positions. A two-pronged attack was then put in by the 1st and 3rd Battalions, 21st Marines. Companies 'A' and 'C' from the 1st Battalion attacked the position from the northwest, while Companies 'L' and 'K' from the 3rd Battalion attacked from the south. This proved successful as the defenders had been forced from their dug-outs by the earlier artillery fire and air strikes, making them easier targets for the Marines. The previous strikes had also had the effect of clearing some of the vegetation, which made the going easier for the Marines during the attack.
In capturing Hellzapoppin Ridge, the Marines lost 12 men killed and 23 wounded. Japanese losses were at least 50 killed. The morning after the attack, the 1st Battalion, 21st Marines exploited the position as far east as the Eagle River – which flowed into the Torokina – where they began work on constructing defensive works to consolidate their position.
Battle of Hellzapoppin Ridge and Hill 600A