Complex sentence: In late December, the 20th Brigade, which had been largely rested during the advance on Wareo, took over from the 4th, and sweeping up the coast against light Japanese resistance they captured Sio in early January 1944, having suffered only very light casualties.
Split into simpler sentences: In late December, the 20th Brigade, which had largely been rested during the advance on Wareo, took over from the 4th. After sweeping up the coast quickly against light Japanese resistance, they captured Sio in early January 1944, having suffered only very light casualties.