Beachhead

[Zipporah Schumaker]

an area of land near the sea or a river that an attacking army has taken control of and from where it can move forward into enemy country:

[Tanya Shivari]

a position in a market that a company achieves and that it hopes to make stronger in the future:

[Tina]

A defended position on a beach taken from the enemy by landing forces, from which an attack can be launched.