* General known for sensitive work with Iraqi tribal sheikhs
* First Marine to be deputy commandant of Naval Academy
* Allen is married with two daughters
By David Alexander
WASHINGTON, Nov 13 (Reuters) - Marine Corps General John Allen, the soberly formal, spit-and-polish head of U.S. and international forces in Afghanistan, is not a military leader whose image immediately conjures up the word "flirtatious."
The four-star general, who succeeded General David Petraeus last year as head of the International Security Assistance Force, is known for his ability to work with tribal sheikhs, a skill that helped him turn the tide against al Qaeda in Anbar Province in Iraq five years ago and has served him well in Afghanistan.
So the news that Allen, a 36-year veteran of the Marine Corps, had been snared in the same investigation that prompted the resignation of Petraeus as CIA director last week was greeted with surprise at the Pentagon and elsewhere in Washington.
John Ullyot, who served under Allen at Camp Lejeune in North Carolina in 1993, said he was all about "setting the example" for those under him and it was "hard for anyone who ever served under Allen" to believe he had been pulled into the probe.
Allen, who is married and has two daughters, "was known as a kind of warrior monk," said Ullyot, who was a spokesman for former U.S. Senator John Warner, a Republican who chaired the Senate Armed Services Committee.
Allen's connection to the probe that snared Petraeus was revealed early on Tuesday when Defense Secretary Leon Panetta announced he was putting Allen's nomination as head of U.S. European Command on hold pending an investigation.
A senior U.S. defense official said Panetta had asked the Defense Department's inspector general to investigate what the Pentagon called "inappropriate communication" between Allen and Jill Kelley, a Tampa, Florida socialite who is involved in volunteer causes that support the military.
Kelley is the woman who told the FBI she had received anonymous harassing emails about Petraeus. The FBI investigation into the emails uncovered an extramarital affair between Petraeus and his biographer, Paula Broadwell, who was fou nd to be the source of the emails to Kelley, officials have said.
The FBI investigation also uncovered 20,000 to 30,000 pages of emails between or copied to Allen and Kelley. While defense officials were unable to say exactly how many emails there were between the two, the volume in pages raised concerns, they said.
A senior defense official, speaking on condition of anonymity, said the emails were "flirtatious" in nature, but did not deal with security or military business. The official said he had not seen the emails and could not say whether they were merely friendly or sexually explicit.
The investigation came just two days before Allen, the first Marine to serve as C ommandant of Midshipmen at the U.S. Naval Academy, was to testify at a confirmation hearing naming him to replace Admiral James Stavridis as head of the U.S. European Command and Supreme Allied Commander Europe.
Allen and Petraeus have long known one another and served together. Allen was Petraeus' deputy at U.S. Central Command, based in Tampa.
Petraeus personally recommended Allen for the ISAF command. D uring A llen's c onfirmation hearing for the job, S ena tor John Mc Cain told Allen he could "think of no higher compliment to pay a military officer" than to have the kind of support Petraeus had given him.
Allen has served as the head of ISAF since July 2011, managing the drawdown of U.S. forces following a surge that helped push Taliban insurgents out of major cities across the country.
His time in Afghanistan also has been marked by a spate of incidents that have enraged Afghans. They include video images of troops urinating on Taliban corpses and the burning of Korans and religious texts taken from a prison library. There also has been a surge in attacks on international forces by their Afghan partners.
Allen has handled the incidents with sensitivity, even as tensions have increased, h is s upporters say.
"I think General Allen has done a good job under very difficult circumstances in Afghanistan," said Senator Susan Collins, a member of the Armed Services Committee.
McCain, the top Republican on the Armed Services Committee, said he was surprised by the probe of Allen's emails and urged people to withhold judgment until the inspector general had finished his investigation.
"I have great respect and appreciation for the work that General Allen has done," he said. "If we fail in Afghanistan, which we are, it's because of decisions that were made by the president, not by General Allen."
"General Allen has said that he is not guilty of any improper behavior," McCain added. "He deserves to have us withhold judgment until the investigation is completed."
Allen, a 1976 Naval Academy graduate, served from 2008 to 2011 as deputy commander of U.S. Central Command, which oversees U.S. military dealings with countries from Egypt to Kazakhstan, including Afghanistan and Pakistan.
He was a deputy commanding general of the 2nd Marine Expeditionary Force in Iraq from 2006 to 2008.