reinforcement [reinforcements](in plural: additional troops or materiel sent to support a military action) noun [UK: ˌriːɪn.ˈfɔː.smənt] [US: ˌriən.ˈfɔːr.smənt]
succour [succours](aid or assistance in the form of military equipment and soldiers) noun [UK: ˈsʌkə(r)] [US: ˈsʌkər]