Although triremes were meant to be rowed in battle, each ship had a mast and sail that were used when there was a considerable distance to go and a wind on the stern quarter. If a battle was expected, the bulky mast and sail were left on shore. In fact, it was so much the custom for early warships to leave the sails and masts ashore, that carrying them into battle, even though they were stowed below, was regarded as a sign of cowardice, since it implied the intention to leave the battle early. Mark Antony's decision to take sails along into the great naval battle at Actium, in which he and Cleopatra VII were defeated by Octavian, is said to have demoralized his forces and contributed to his losing that battle.
Willard Bascom, Deep Water, Ancient Ships: Treasure Vault of the Mediterranean