British armed trawlers performed anti-submarine work in both world wars. A vessel without ASDIC or sonar could still contribute if another ship directed its attack. In this example, the sonar-equipped ship maintains contact while the trawler carries out the depth-charge run. Limited equipment need not make an additional hull useless. The criticism of Japan is that it accepted such practical compromises only when wartime pressure forced the issue, after pursuing more complete solutions.
Notable Point · 1:03:13-1:04:15
Armed trawlers as useful additions to an escort group
An armed trawler without sonar could still make a depth-charge run directed by a ship holding contact.