IPA: /ˌɪntərˈsɜːrvɪs/
KK: /ˈɪntərˌsɜrvɪs/
Relating to or involving cooperation and relationships between different branches of the military.
The interservice exercises helped improve coordination among the army, navy, and air force.
Interservice → It is formed from "inter-" (meaning between) and "service" (from Latin "servitium", meaning service or slavery). The word refers to activities or cooperation that occur between different services, particularly in a military context.
Think of activities that happen 'between' ('inter-') different 'services' — that's what interservice means.