beach-head

/B IY1 CH EH0 D/
noun
  1. 1

    An area of hostile territory (especially on a beach) that, when captured, serves for the continuous landing (or movement into position) of further troops and material

  2. 2

    (by extension) An initial success that ensures the possibility of further advances in a project; a foothold.

Source: https://en.wiktionary.org/wiki/beach-head, https://en.wiktionary.org/wiki/beachhead