Synonyms for Foothold (same or very similar meaning)
WordNet sense 1 (an area in hostile territory that has been captured and is held awaiting further troops and supplies):
bridgeheadWordNet sense 2 (a place providing support for the foot in standing or climbing):
footingWordNet sense 3 (an initial accomplishment that opens the way for further developments):
beachheadFrom the ODE community, based on WordNetadd/edit