Complex sentence: The battle took place at the end of the ground campaign on Vella Lavella, as the Japanese sought to evacuate the 600-strong garrison from the island, which had become hemmed into a small pocket on the northern end of the island around Marquana Bay.
Split into simpler sentences: The battle took place at the end of the ground campaign on Vella Lavella, as the Japanese sought to evacuate the 600-strong garrison from the island. The garrison had become hemmed into a small pocket on the northern end of the island around Marquana Bay.