A convoy could attract submarines while carrying enough escorts to attack them. With limited protection, an escort might force a submarine underwater and then hurry back to the merchant ships. A stronger escort could pursue a contact with depth charges and mortars for long enough to destroy it. Submarine losses also tended to remove the crew because serious underwater damage could lead to flooding and collapse below crush depth.
Notable Point · 1:05:00-1:06:26
How a convoy escort could hunt submarines
Enough escorts allowed a convoy to draw submarines into sustained attacks instead of merely forcing them away.