Eight Russian military planes and four navy vessels, including two submarines, have come close to Alaska in the past week as Russia and China conducted joint military drills. None of the planes breached U.S. airspace and a Pentagon spokesperson said Tuesday there was no cause for alarm.

“It’s not the first time that we’ve seen the Russians and the Chinese flying, you know, in the vicinity, and that’s something that we obviously closely monitor, and it’s also something that we’re prepared to respond to,” Pentagon spokesperson Maj. Gen. Pat Ryder said at a news conference.

As part of a "force projection operation,” the Army on Sept. 12 sent the soldiers to Shemya Island, some 1,200 miles (1,930 kilometers) southwest of Anchorage, where the U.S. Air Force maintains an air station that dates to World War II. The soldiers brought two High Mobility Artillery Rocket Systems, or HIMARS, with them.

U.S. Sen. Dan Sullivan, R-Alaska, said the U.S. military also deployed a guided missile destroyer and a Coast Guard vessel to the western region of Alaska as Russia and China began the “Ocean-24” military exercises in the Pacific and Arctic oceans Sept. 10.

The North American Aerospace Defense Command said it detected and tracked Russian military planes operating off Alaska over a four-day span. There were two planes each on Sept. 11, Sept. 13, Sept. 14 and Sept. 15.

The planes operated in the Alaska Air Defense Identification Zone, a zone beyond U.S. sovereign airspace, but within which the U.S. expects aircraft to identify themselves, NORAD said.