Close, point, area and interdiction defence

Close defence brings every available weapon to bear against an aircraft at very short range. Point defence is the immediate contest between a ship and the threat attacking it. Area defence combines the protection provided by a task group, while interdiction uses fighters or other means to disrupt an attack farther away. Detection should extend beyond the interception zone so the force has time to arrange its defence or manoeuvre. These labels do not have fixed distances across every period or service. Operating inside a fjord also imposes different limits from operating in the open ocean. By 1936, naval close range is put at about 4.5 kilometres, illustrating why the same label can mean different distances on land and at sea.