(CNN) The first US service member has died from the novel coronavirus, the US military announced on Monday.

An Army National Guardsman from New Jersey passed away on Saturday, according to a statement from the Department of Defense. Gen. Joseph Lengyel, the chief of the National Guard Bureau, identified the service member as Army Capt. Douglas Linn Hickok.

"Our thoughts are with his family & friends. All of us are likely to know people directly affected by this virus in the coming weeks," Lengyel said on Twitter. "As our nation fights its greatest challenge in recent memory, we're all going to need to draw on our inner strength & resilience to win this war & comfort those in pain. We must bring our best selves every day to overcome this as fast as possible for our great country."

Hickok had been hospitalized since March 21.

"Today is a sad day for the Department of Defense as we have lost our first American service member -- active, reserve or Guard -- to Coronavirus," Secretary of Defense Mark Esper said in the statement, which was released before Lengyel identified Hickok.

"This is a stinging loss for our military community, and our condolences go out to his family, friends, civilian co-workers and the entire National Guard community. The news of this loss strengthens our resolve to work ever more closely with our interagency partners to stop the spread of COVID-19."

News of Hickok's death comes as coronavirus cases within the US military continue to mount, surpassing 600 as of Monday morning. Twenty-six of those cases required hospitalization, according to the Defense Department. Thirty-four service members have recovered from their illness.

A US military dependent and defense contractor had died as a result of the virus, and the total number of cases involving the Department of Defense surpassed 1,000 on Monday.

The surging cases are the latest signs that the virus has become a national security challenge.

Beyond its spread within the armed forces, top US commanders around the globe had previously expressed concerns that as allies shut down borders and travel, there's a risk that military readiness may start degrading, according to several defense officials.

Still, the Department of Defense stressed in a news release Monday that it has "adopted dramatic mitigation measures to protect service members, civilian employees, contractors and their families from Coronavirus."

"These include mandating social distancing, termination of certain work and training activities and providing testing and care for our community members."

Concerns about the pandemic's spread drove the US Marine Corps to temporarily suspend basic training for 50% of its new enlisted recruits on Monday, and the Pentagon is increasingly preparing for the possibility of wider outbreaks across the force than originally anticipated.

CNN reported earlier this month that the US Army is suspending "non-mission essential functions," including some non-critical training of units in the field and physical fitness training involving large numbers of troops, according to an internal Army directive that was obtained by CNN.

"Mitigation measures taken by the Army to blunt the spread of COVID-19 have proven insufficient," the internal order said.

This story has been updated with additional information Monday.