In 1990, he earned the William P. Clements Award as military instructor of the year, and left to direct the Infantry Officer Course at the Basic School.
Iraq and Afghanistan.
Allen succeeded Gen. David Petraeus as commander of U.S. Central Command in 2010 and as commander of the International Security Assistance Forces in Afghanistan in 2011.
In Iraq, Allen won praise for ability to work with tribal leaders in the volatile al-Anbar province. He is credited with holding the mission in Afghanistan together amid several challenges. The burning of Korans by U.S. troops and images of Marines urinating on the corpses of Taliban fighters enraged Afghans, and attacks on international forces by the Afghan fighters they're supposed to be training have increased.
Admired by Republicans and Democrats, he was seen as a lock to win confirmation to head U.S. European Command until the FBI discovered the alleged emails to Kelley. Agents discovered the messages while investigating harassing emails to Kelley, allegedly from 40-year-old Paula Broadwell, Petraeus' biographer and reported mistress.
Petraeus, the architect of the surges in Iraq and Afghanistan, acknowledged an affair and resigned as director of the CIA last week.
Panetta has ordered the Defense Department's inspector general to investigate Allen based on communications the FBI has given to the Pentagon. But in his first public comments on the matter, he told reporters in Perth, Australia, Wednesday that "no one should leap to any conclusions here."
Panetta said Allen "certainly has my continued confidence to lead our forces and to continue the fight."
The Associated Press contributed to this article.