What is the meaning of foothold?

noun

• An area in hostile territory that has been captured and is held awaiting further troops and supplies.
  • usage: "an attempt to secure a bridgehead behind enemy lines"; "the only foothold left for British troops in Europe was Gibraltar"
  • synonyms: bridgehead
• A place providing support for the foot in standing or climbing.
  • synonyms: footing
• 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: beachhead