What is the meaning of beachhead?

noun

• A bridgehead on the enemy's shoreline seized by an amphibious operation.
  • usage: "the Germans were desperately trying to contain the Anzio beachhead"
• An initial accomplishment that opens the way for further developments.
  • usage: "the town became a beachhead in the campaign to ban smoking outdoors"; "they are presently attempting to gain a foothold in the Russian market"
  • synonyms: foothold