Complex sentence: Between 10 and 16 January, the Okabe Detachment moved down the coast in barges to Salamaua, where it assembled and completed its preparations for the attack on Wau.
Split into simpler sentences: Between 10 and 16 January, they moved down the coast to Salamaua in barges. The Okabe Detachment assembled at Salamaua and completed its preparations for the attack on Wau.