The 2/30th Battalion's commanding officer, Lieutenant Colonel Frederick "Black Jack" Galleghan,[3] was ordered to mount an ambush on the main road, 11 kilometres (6.8 mi) west of Gemas in the hope of preventing the Japanese from advancing any further south.

[4] The ambush site was located at a point where a wooden bridge crossed the Sungei Gemencheh river, connecting Gemas with the larger neighbouring town of Tampin, and bringing traffic on the road into a long cutting through thick bushland.

[3] The Japanese had passed through Tampin and needed to cross the bridge to reach Gemas and at 16:00 on 14 January 1942, "B" Company 2/30th Battalion under Captain Desmond Duffy, initiated the ambush.

As the Japanese passed through the engagement area in their hundreds—many of them on bicycles—the bridge was blown and the Australians opened fire with machine guns, rifles and grenades.

According to Coulthard-Clark, total Japanese casualties in the wider battle numbered over 800, while the Australians lost more than 88 killed, wounded or missing;[1][6] Despite the tactical victory at Gemas, and strong stands later at Bakri, the 22nd Australian Brigade’s ambush north of Jemaluang and the fighting withdrawal from Muar, the Japanese advance down the Malay Peninsula was only temporarily slowed.