People began to feel ill with symptoms of sore throats and nosebleeds after mail was opened containing an unknown substance at the U.S. Marine Corps headquarters
Nearly 7,000 U.S. troops are taking part in the 37th Cobra Gold drills held in Thailand.
The Kremlin has vowed it will not be caught off guard if war breaks out.
The branch's top commander said he is also considering making promotions conditional on marines undergoing refresher training.
The U.S. Marine Corps said the incident was under investigation but gave no additional information.
The closed network solicited nude photos of female service members, some of whom had their name, rank and duty station listed.
Deployment to Helmand province will be the Marines first since they left in 2014.
Annual remembrance honors members of all branches of military service.
The armies of France, Germany, Great Britain, Italy and Japan are smaller than the Marine Corps.
The U.S. Marines were taking part in a training exercise at the camp in North Carolina.
Three were wounded in a shooting by a machine gun-toting attacker on a high-speed train between Amsterdam and Paris.
The intelligence of officers in the Marines has steadily and significantly declined over the last 34 years.