By Andrea Shalal
WASHINGTON (Reuters) - Last spring, U.S. Marine Corps Commandant General James Amos did not even know who Sheryl Sandberg was.
Six months later he is good friends with Sandberg, the chief operating officer of social media company Facebook Inc <FB.O>, a top advocate for empowering women to take on leadership roles.
Amos, who retired Friday after 44 years of service, met Sandberg in March, and has since hosted her and other Facebook executives at several events aimed at brainstorming ways to boost the number of female Marines from the current 7.5 percent.
"The relationship is very strong. I think the world of her. It's based on mutual respect for leadership and character development," the four-star general and former pilot told Reuters at his Pentagon office days before his retirement.
Women account for about 15 percent of the entire active duty U.S. military. Their representation in the Marine Corps has been lower than the other services, but that may change as more front-line combat jobs are opened to women, beginning in 2016.
The Pentagon has also launched a fresh drive to end sexual assault in the military and review its alcohol policy, amid a series of embarrassing incidents in which officers have been accused of tolerating and even encouraging sexual misconduct.
Amos began reaching out to female executives this spring as the Marine Corps grappled with decisions about opening ground combat roles to women, stamping out sexual assaults, and how the smallest military service could attract and retain more women.
He first met with Marillyn Hewson, chief executive of Lockheed Martin <LMT.N>, and then Linda Hudson, the former CEO of the U.S. unit of Britain's BAE Systems Plc <BAES.L>, two executives who worked their way up the ladder in the male-dominated weapons industry.
"They helped me see what I'm not seeing, simply because I'm a guy, and as my wife tells me, an old, white guy," Amos said.
Amos also went to Bentonville, Arkansas to meet with Gisel Ruiz, executive vice president and chief operating officer of Wal-Mart Stores Inc <WMT.N>, and other Wal-Mart executives.
When they asked him if he knew about Sandberg and her bestselling book "Lean In: Women, Work and the Will to Lead," Amos says, "I had to display my 'cave man' prowess and say no."
But he quickly caught up by reading the book, watching Sandberg's 2010 famous talk to the TED group about women in leadership, and finally meeting with her at Facebook's headquarters in Menlo Park, California.
Since then, Sandberg has twice visited the Marines' officer candidate school to meet with future leaders. Amos also asked all 15 three-star generals in the Marines, all male, to read Sandberg's book ahead of a meeting with her at the Pentagon.
"She hit it out of the park," he said, as he described the impact of Sandberg's firsthand account of her experiences as one of the very few women at the C-level of business.
Facebook declined to comment.
Amos said the outreach to corporate leaders has prompted new discussions among Marine Corps officials about how to encourage women stay in the military even when they decide to have children, and other ways to promote leadership among women.
Several months ago, he convinced a female major who was thinking of quitting to stay in the service by helping her get a transfer together with her husband, who is also a Marine.
"It was a small thing, but it's important," he said, noting that a dearth of young women officers was reducing the size of the "bench" for future leaders.
The Marine Corps has also set up a special office to focus on "talent management" and coordinate a range of diversity efforts under way across the service. It is also reviewing standards for a wide range of jobs as it prepares to comply with the Pentagon's 2013 decision to open combat roles to women.
Bringing in Sandberg has generated important discussions among Marines, one female officer told Reuters.
"You'd think our sectors would be very different, but we face a lot of the same challenges. Sheryl told us that when she looks across her company, she looks five lines deep and there is not a woman in sight."
(Reporting by Andrea Shalal; Editing by Ros Krasny and Meredith Mazzilli)