On the night of 15 January, the Japanese captured a number of barges moored on the southern bank of the Muar river and towed them overstream to flank both the town of Muar and the Indian garrison's only reserve battalion. Packed barges and junks were making their way across the river mouth, meeting no resistance except a subsequent brush with an Indian patrol, which retired after a brief exchange of shots. The patrol never alerted headquarters that the Japanese were on the south bank. As day broke, the outflanking force surprised a company of the 7/6th Rajputana Rifles, and routed them. The remaining three Indian companies (two from the 18th Royal Garhwal Rifles and another from the Rajputana Rifles) on the north bank were cut off and captured soon after, without the main garrison at Muar even realising that an entire Japanese division was on the other side of the river. By noon, they were attacking from upstream both Muar Town and the garrison's line of communications with its only reserve battalion, 4/9th Jat Regiment, which was located near Bakri, on the main road south from Muar.