 Under Caesar, an invasion fleet was assembled in the English Channel to allow the invasion of Britain; under Pompey, a large fleet was raised in the Mediterranean Sea to clear the sea of Cilician pirates.During the civil war that followed, as many as a thousand ships were either constructed or pressed into service from Greek cities.By the time of Julius Caesar in 54 BC, regular legionary units were supplemented by "exploratores", a body of scouts, and "speculatores", spies who infiltrated enemy camps.