What is the meaning of intervene?

verb

• Get involved, so as to alter or hinder an action, or through force or threat of force.
  • usage: "Why did the U. S. Not intervene earlier in WW II"
  • synonyms: step in, interfere, interpose
• Be placed or located between other things or extend between spaces and events.
  • usage: "This interludes intervenes between the two movements"; "Eight days intervened"
• Occur between other event or between certain points of time.
  • usage: "the war intervened between the birth of her two children"