How an escorted convoy can become a submarine trap

Grouping many merchants permits escorts to be concentrated rather than dispersed among tiny formations. One example places forty or fifty merchants with a close escort and a separate hunter-killer element. A convoy that attractive can tempt a submarine into contact, after which spare escorts can remain over it until First World War limits on submerged endurance force it to surface. Merchant hulls can be mass-produced and their surviving crews reused, whereas a lost submarine usually takes its trained crew with it. Repeated interceptions therefore erode the attacker's experience as well as its boat inventory.