Battle of Mount Austen, The Galloping Horse, and The Sea Horse - Battles of The Galloping Horse, The Sea Horse, and Second Mount Austen

Battles of The Galloping Horse, The Sea Horse, and Second Mount Austen

On 2 January, with the arrival of the U.S. Army's 25th Division and the rest of the U.S. Marine 2nd Division, all of the American units on Guadalcanal and Tulagi were together designated as the XIV Corps with Patch in command. Sebree took over as commander of the Americal Division. On 5 January, Patch issued his plan to begin operations to clear Guadalcanal of Japanese forces. The 2nd Marine Division was to push westward from the Matanikau River along the coast while the 25th Division was to finish clearing Mount Austen and to secure the hilltops and ridges located around the inland forks of the Matanikau. The Americal Division and the 147th Regiment would guard the Lunga perimeter.

The deep river ravines of the Matanikau's upper forks naturally divided the U.S. 25th Division's operations area into three distinct areas, with one main terrain feature dominating each area. East of the Matanikau was Mount Austen. In the wedge between the southeast and southwest forks of the Matanikau Hills 44 and 43 together formed a terrain feature that the Americans called the "Sea Horse", because of its shape when viewed from above. Between the Matanikau's southwest and northwest forks was a much larger hill mass labelled, also because of its shape, the "Galloping Horse".

Major General J. Lawton Collins—commander of the 25th Division—assigned his 35th Infantry Regiment to clear the Gifu, secure the rest of Mount Austen, and to capture the Sea Horse. He ordered the 27th Infantry Regiment to seize the Galloping Horse from the north. The 35th and the 27th were then to link up on Hill 53 (the Galloping Horse's "Head") to finish clearing the nearby hills and ridges. Collins placed his 161st Infantry Regiment in reserve. Ammunition and supplies for the attacking troops would be transported along rough jeep trails as far forward as possible and then carried the rest of the way by native Solomon Islanders.

Having observed the arrival of the American reinforcements to the island, the Japanese were expecting the offensive. Hyakutake ordered the units on the hilltops around the Matanikau and in the Gifu to hold in place in their prepared positions. The Japanese hoped that as the Americans surrounded and intermingled with the Japanese defensive pockets that the close quarters fighting would prevent the Americans from employing their superior firepower in artillery and close air support. At night, the Japanese planned to infiltrate the American rear areas and interdict their supply lines to prevent the American assault forces from receiving sufficient ammunition and provisions to continue their attacks. The Japanese hoped to delay the Americans long enough for more reinforcements to arrive from Rabaul or elsewhere.