Washington ? May was the deadliest month of the Iraq war for part-time American servicemen.

Thirty-one of them died: 14 members of the Army National Guard, 12 from the Marine Corps Reserve, four from the Army Reserve and one Navy Reserve hospital corpsman attached to a Marine combat unit.

The overall U.S. death toll in Iraq last month – counting active-duty as well as mobilized reserve forces – was 80. That is the highest for any month since January, when 107 died as insurgent attacks rose sharply prior to the Iraqi election. Fifty-two died in April and 36 in March, when it appeared the insurgency was waning.

Iraqis bore the brunt of insurgent violence in May, but it also took a heavy toll on the approximately 140,000 U.S. troops there. The 80 deaths compares with a monthly average of 70 over the previous 12 months.

The death toll among the Guard and Reserve underscores an important aspect of their recruiting problems: More potential recruits, citing concern about being sent to the war zone, are opting for other careers. The Army Guard missed its recruiting target last year and has fallen even farther behind this year.

An honor guard removes the casket of Mississippi National Guard Sgt. Audrey Lunsford, 29, Thursday in Batesville, Miss. Lunsford, a member of the 155th Brigade Combat Team, was killed in Iraq when his vehicle was hit by an explosive device. May was the deadliest month of the Iraq war for members of the National Guard and Reserves.

The previous worst months for Guard and Reserve deaths in Iraq were January, when 30 died, and last November, with 28. Those also happened to be among the deadliest months overall for American forces in Iraq.

The 12 deaths among Marine reservists in May was the most for any month of the war.

Eight of the 12 Marines were with the same unit – the 3rd Battalion, 25th Marine Regiment of the 4th Marine Division.

It participated in a weeklong combat operation dubbed Operation Matador that targeted hide-outs, staging areas and infiltration routes for insurgents and foreign fighters near the Syrian border.

Also killed while operating with that unit was Petty Officer 3rd Class Jeffrey L. Wiener, 32, of Louisville, Ky., a Navy reservist.

Previously, the deadliest month for Marine reservists in Iraq was last November, when an all-out offensive routed insurgent strongholds in Fallujah, west of Baghdad. Eleven Marine reservists died that month.

The National Guard and Reserve, which make up nearly half the force in Iraq, have generally had fewer than 20 deaths per month during the war, and it’s not clear why their losses spiked to 31 in May.