Close escort and distant cover in convoy defence

What is the difference between close convoy escort and distant cover?

Close escorts defend a convoy against submarines and air attack; distant carriers and heavy ships cover wider routes and deal with surface raiders.

The immediate convoy screen differs from a heavier force positioned to cover a wider sea area. Destroyers, corvettes, and an escort carrier remain with a particular convoy to find submarines and defeat air attack. Fleet carriers, battleships, and heavy cruisers can stand farther away to meet a surface raider such as Scharnhorst or Tirpitz. Because those capital ships are scarce, one distant force can be positioned to support more than one convoy moving through the region. A modern version could distribute systems among merchant ships and use numerous uncrewed escorts under a small number of frigate command ships. A carrier group with airborne early warning would still provide the broader distant cover. The two layers solve different threats, so treating either one as a substitute for the other leaves a gap in convoy defence.