[3][4] For the Japanese, New Georgia formed a key part in their defenses along the southern approaches to Rabaul, and they sought to defend the area strongly, moving reinforcements by barge along the Shortlands–Vila–Munda supply line.

These would then be garrisoned to support the movement of troops and supplies from Guadalcanal to Rendova, which would be built up as base for further operations in New Georgia focused on securing the airfield at Munda.

After linking up with a small party of local guides and a reconnaissance force that had been sent ahead, these troops consolidated their position and then moved to the mainland to begin scouting the area around Zanana towards the Barike River, and also between the Japanese airfield at Munda Point and Bairoko Harbor.

To support this effort, a company of the 4th Marine Raider Battalion had been scheduled to reinforce the 169th Infantry Regiment, but they were unable to be released from operations to secure Segi Point and Viru Harbor.

[10] Commanded by Colonel Genjiro Hirata, the Japanese forces defending Munda consisted of several battalions from the 229th Infantry Regiment as well as artillery, engineer, signals and medical support elements.

[12][13] On 4 July, the U.S. troops undertook a preliminary move prior to beginning their advance, marching towards a line of departure along the Barike River about 3 miles (4.8 km) away.

[14] Meanwhile, on the northern coast of New Georgia, a force of U.S. Marines and Army troops landed at Rice Anchorage in an effort to block the movement of Japanese reinforcements down the Munda trail.

[16] The terrain between the landing beach at Zanana and the objective at Munda Point was not conducive to a quick approach, and U.S. planners had failed to appreciate the difficulty the troops would have traversing the single, narrow track or through the dense jungle, which was crossed by fast flowing creeks and streams, and flanked by rocky ridges and deep ravines.

[16][17] In an effort to breakthrough, on 9 July, Hester ordered the 172nd Infantry Regiment to carry out a flanking move to the north to attack the Japanese position in the rear, while the 169th Infantry Regiment continued its frontal assault; although the attack was supported by heavy artillery, naval gunfire support and air strikes,[16] Sasaki correctly appreciated the U.S. commander's intent and responded quickly to the attack, moving troops to counter the flanking move, while in the forward areas movement was held up by Japanese snipers who concealed themselves in baskets in the trees and fired upon the U.S. troops with flashless rifles.

The following day, the 3rd Battalion, 169th Infantry Regiment gained the south ridge—later dubbed "Reincke Ridge"—after several hours of fighting supported by dive bombers and artillery.

The following day, a second landing was carried out at Laiana, in an effort to shorten lines of supply and bring in reinforcements from the 3rd Battalion, 103rd Infantry Regiment, which linked up with the 172nd.

[16] As part of efforts to break through to the cut-off 169th, the U.S. Army 118th Engineers, having previously pushed a track from Zanana, bridged the Barike River and ran a jeep trail towards the 169th's lines.

The preparations would take time, though, which the Americans sought to buy with harassing fire from artillery and air strikes, coupled with minor advances aimed at securing some of the trails between Laiana and Zanana to relieve the 169th.

[27][28] The U.S. offensive made small gains because of the limited combat experience by its soldiers, poor leadership by inexperienced U.S. Army officers, harsh terrain and conditions on New Georgia, and effective defensive measures by the Japanese.

Before this could begin, though, the Japanese launched a counterattack on 17 July using the reinforcements that had arrived from Vila, effectively bringing the Allied drive on Munda temporarily to a halt.