Convoy

A convoy is a group of merchant ships sailing together under the protection of naval escorts, a tactic that concentrates defense and forces an attacker to engage the screen first. Convoying broke the U-boat campaigns of both world wars; in the Atlantic from 1917 and again after 1939 it cut sinkings sharply by grouping ships behind destroyers, corvettes, and escort carriers. Under the law of naval warfare, neutral merchant ships convoyed by neutral warships of their flag are exempt from visit and search if the escort commander certifies their cargo.