Complex sentence: He sailed back to France the following winter, under orders from the marquis to obtain additional military resources for the colony; during this crossing, he continued familiarising himself with the ways of the sea, skills that would later serve him well.
Split into simpler sentences: He sailed back to France the following winter, under orders from the marquis to obtain additional military resources for the colony. During this crossing, he continued to learn about the ways of the sea, skills that would later serve him well.