US deploys 3,500 Marines to Middle East amid rising tensions with Iran.

The U.S. has deployed approximately 3,500 Marines and sailors to the Middle East amid rising tensions with Iran, which has warned that any ground incursion would be a "Welcome to Hell." The buildup, including the arrival of the USS Tripoli, adds to a regional force of roughly 50,000 troops and comes as officials weigh further military options.