Ballistic missile flight creates distinct interception windows

A ballistic missile is vulnerable in different ways across boost, midcourse, and re-entry. Launch is slow and comparatively predictable but often occurs deep inside defended territory or at sea; midcourse offers another predictable arc; re-entry compresses reaction time and may introduce multiple vehicles and decoys. British systems are cited as combining active payloads with devices intended to create misleading sensor returns. The strategic difficulty comes from the volume major powers can launch as well as the velocity of each missile.