"The people making this decision are doing so as part of another social experiment, and they have never lived nor fought with an infantry or Special Forces unit," Boykin said in a statement released by the conservative Family Research Council, for whom he now works.
"These units have the mission of closing with and destroying the enemy, sometimes in close hand-to-hand combat. They are often in sustained operations for extended periods, during which they have no base of operations nor facilities. Their living conditions are primal in many situations with no privacy for personal hygiene or normal functions."
Integrating the genders in direct-combat situations "places additional and unnecessary burdens on leaders at all levels," Boykin said. "While their focus must remain on winning the battles and protecting their troops, they will now have the distraction of having to provide some separation of the genders during fast moving and deadly situations.
"Is the social experiment worth placing this burden on small unit leaders? I think not," he concluded. Boykin is a former deputy undersecretary of defense for intelligence who worked with the CIA in the 1990s.
Outgoing Defense Secretary Leon Panetta, in one of his last official acts, is expected to announce Thursday that more than 230,000 battlefront posts — many in Army and Marine infantry units and maybe in elite commando jobs — are now open to women.
The historic change, which was recommended by the Joint Chiefs of Staff, overturns a 1994 rule prohibiting women from being assigned to smaller ground combat units.
Some jobs may open as soon as this year, while decisions on others, such as special operations forces, may take longer, the Associated Press reported. Military service chiefs will have until January 2016 to make the case that some positions should remain closed to women.
Officials briefed The Associated Press on the changes Wednesday on condition of anonymity so they could speak ahead of the official announcement.
The new order expands the Defense Department's order of nearly a year ago to open about 14,500 combat positions to women, nearly all of them in the Army.
Women comprise about 14 percent of the 1.4 million active military personnel, the AP reported. More than 280,000 women have been sent to Iraq, Afghanistan or to jobs in neighboring nations in support of the wars. Of the more than 6,600 U.S. service members who have been killed, 152 have been women.
A long-time critic of women in combat says direct ground-combat missions pose physical demands that are beyond the capability of almost all women.
Elaine Donnelly, president of the Center for Military Readiness, served as a member of the 1992 Presidential Commission on the Assignment of Women in the Armed Forces:
A year ago, she called it a mistake to treat the military like just another civilian equal-opportunity employer.
"If a soldier is wounded in battle...a collocated support soldier may be the only person in a position to evacuate the wounded soldier on his own back. In this environment, women do not have an equal opportunity to survive, or to help fellow soldiers survive. Lives should not be put at needless risk just to satisfy 'diversity metrics' for the career ambitions of a few."