U.S. air defense forces are being deployed to Saudi Arabia | “The president has approved the deployment of U.S. forces, which will be defensive in nature,” Esper said at the Pentagon.

https://www.latimes.com/politics/story/2019-09-20/u-s-air-defense-forces-being-deployed-to-saudi-arabia

https://www.cnbc.com/2019/09/20/the-pentagon-will-deploy-us-forces-to-the-middle-east-on-the-heels-of-the-iranian-attack-on-saudi-arabian-oil-facilities.html

Saudi Arabia Owns the 45th Floor of Trump Tower, and It Shows
https://truthout.org/articles/saudi-arabia-owns-the-45th-floor-of-trump-tower-and-it-shows/

Defense Secretary Mark Esper and Gen. Joseph Dunford announce "The President has approved the deployment of U.S. forces, which will be defensive nature and primarily focused on air and missile defense" to Saudi Arabia. Watch the briefing online -- https://www.c-span.org/ 
https://twitter.com/cspan/status/1175199093926322176