Among the many historic changes in the Defense Department in 2011 was the transition in leadership as Robert M. Gates stepped down after serving as defense secretary from December 2006 through June 2011. Leon E. Panetta was sworn in as the 23rd defense secretary on July 1, 2011. Here’s a look back at some of the top headlines related to the transition.

Panetta Pledges ‘No Hollow Force’ on His Watch

WASHINGTON, July 1, 2011 - New Defense Secretary Leon E. Panetta pledged there will be no hollow force on his watch and vowed to be a tireless advocate for service members and their families. The secretary made the commitment in a message to the Defense Department released after he took the oath of office on the morning of July 1, 2011. Story | Special

Gates Sends Message Thanking Troops for Service

WASHINGTON, June 29, 2011 – Secretary of Defense Robert M. Gates has sent a message to every post, ship, base and installation thanking service members and their families for their service. Story | Special

Following on the heels of the swearing-in of the new defense secretary, Navy Adm. Mike Mullen stepped down as chairman of the Joint Chiefs of Staff. As “Team Mullen,” the chairman and his wife, Deborah, championed the needs of service members and their families. Army Gen. Martin E. Dempsey was sworn in as the 18th chairman on Sept. 30, 2011. Here’s a look back at some of the top headlines related to the transition.

Dempsey Settles in as Chairman Behind MacArthur’s Desk

WASHINGTON, Oct. 3, 2011 – Army Gen. Martin E. Dempsey, the new chairman of the Joint Chiefs of Staff, took some time today, his first Monday on the job, to speak with Pentagon reporters. Story | Special

Obama Praises Mullen, Welcomes Dempsey as Chairman

WASHINGTON, Sept. 30, 2011 – President Barack Obama today lauded Navy Adm. Mike Mullen during a hail and farewell ceremony here that featured the transfer of responsibilities as chairman of the Joint Chiefs of Staff from Mullen to Army Gen. Martin E. Dempsey. Story | Special

Senior Officials Welcome Troops Home From Iraq

JOINT BASE ANDREWS, Md., Dec. 20, 2011 – President Barack Obama, Vice President Joe Biden, Deputy Defense Secretary Ashton B. Carter and Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, welcomed the final group of U.S. troops home from Iraq here today. Story

Obama: Nation Should Emulate Troops’ Service, Sacrifice

WASHINGTON, Dec. 17, 2011 – The American military exhibits the best the country has to offer, President Barack Obama said in his weekly address today. The last U.S. service members are leaving Iraq after almost nine years of combat. They leave a country and citizenry that has a chance to chart its own course in a tough neighborhood. Story

Panetta Concludes Iraq Mission, Noting Service, Sacrifice

BAGHDAD, Dec. 15, 2011 – Defense Secretary Leon E. Panetta joined Chairman of the Joint Chiefs of Staff Army Gen. Martin E. Dempsey and other U.S. and Iraq leaders in honoring eight years of service and sacrifice as they commemorated the end of the U.S. military mission in Iraq. Story | Special

Panetta, Dempsey to Mark End of Iraq Mission

BAGHDAD, Dec. 15, 2011 – Defense Secretary Leon E. Panetta arrived here today to join Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, in ceremonies marking the end of the U.S. military mission in Iraq. Story | Special

Dempsey: DOD to Stay Engaged, Vigilant in Middle East

ABOARD A MILITARY AIRCRAFT, Dec. 17, 2011 – It’s too soon to calculate how the end of U.S. Forces Iraq will affect the region’s military dynamics, but the U.S. focus on the Middle East and its partner countries there is unwavering, the chairman of the Joint Chiefs of Staff said. Story | Special

Panetta, Dempsey to Mark End of Iraq Mission

BAGHDAD, Dec. 15, 2011 – Defense Secretary Leon E. Panetta arrived here today to join Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, in ceremonies marking the end of the U.S. military mission in Iraq. Story | Special

Panetta Arrives in Afghanistan to Assess Progress

KABUL. Afghanistan, Dec. 13, 2011 – Recognizing what he called a pivotal year in Afghanistan, Defense Secretary Leon E. Panetta arrived here today to thank U.S. service members for their role in reversing momentum against the Taliban, and to assure Afghan leaders of the United States’ continuing commitment as transition moves forward. Story

Allen Welcomes Latest Stage of Afghanistan Transition

KABUL, Afghanistan, Nov. 28, 2011 – The International Security Assistance Force welcomes the release of the Afghan government’s list of areas intended for the second stage of security transition, Marine Corps Gen. John R. Allen, ISAF commander, said in a statement released yesterday. Story

Petraeus: Afghan Transition Will Have Long-term Impact

WASHINGTON, March 16, 2011 – As the transition approaches for Afghan forces to begin taking responsibility for security in their country, actions in the coming months will have consequences for years to come, the commander of NATO and U.S. forces in Afghanistan said here today. Story

Repeal: Quick Reference Guide (PDF)

Oct. 28, 2011 – On December 22, 2010, the President signed legislation that led to the repeal of DADT. The legislation provides that repeal would take effect 60 days after the President, Secretary, and Chairman certify to Congress that the Armed Forces are prepared to implement repeal in a manner that is consistent with the standards of military readiness, military effectiveness, unit cohesion, and recruiting and retention of the Armed Forces. PDF

Obama: Americans No Longer Have to Lie to Serve

WASHINGTON, Sept. 20, 2011 – President Barack Obama today issued a statement on the repeal of the “Don’t Ask, Don’t Tell” law that had barred gay men and lesbians from serving openly in the military. Today, the discriminatory law known as ‘Don’t Ask, Don’t Tell’ is finally and formally repealed. As of today, patriotic Americans in uniform will no longer have to lie about who they are in order to serve the country they love. Story

Defense Leaders Laud Repeal, Return of ‘Equality’

WASHINGTON, Sept. 20, 2011 – The official end today of the “Don’t Ask, Don’t Tell” law reflects the American values that military members uphold, Defense Secretary Leon E. Panetta said today. “Thanks to this change, I believe we move closer to achieving the goal at the foundation of the values that America's all about -- equality, equal opportunity and dignity for all Americans,” he told reporters during a Pentagon news briefing. Story

DOD Set for ‘Don’t Ask, Don’t Tell’ Repeal

WASHINGTON, Sept. 19, 2011 – The repeal of the military’s “Don’t Ask, Don’t Tell” law is slated to take effect tomorrow, a senior Defense Department official told reporters today. Story

Obama Commends Military for Handling of Law’s Repeal

WASHINGTON, July 22, 2011 – The 1993 law that has banned gay men and lesbians from serving openly in the military “undermines our military readiness and violates American principles of fairness and equality,” President Barack Obama said today in announcing he has certified that the armed forces are ready for its repeal. Story

Summary of the DOD Fiscal 2012 Budget Proposal (PDF)

The fiscal 2012 budget supports the department’s security strategy and builds on the changes introduced by the fiscal 2010 defense budget and the fiscal 2011 budget. As in recent years, the budget for fiscal 2012 is organized around four major themes. PDF | Special

Commanders Cite Unpredictable Future Threats

WASHINGTON, March 4, 2011 – America and its allies will face varied and unpredictable security threats in the years ahead, the leaders of the two most intensely engaged U.S. military commands told House Armed Services Committee members yesterday. Story | Special

Continuing Budget Resolution Puts Security at Risk

WASHINGTON, March 1, 2011 – The Defense Department is losing billions of dollars by Congress’ failure to pass the department’s fiscal 2011 budget, putting readiness, modernization and efficiency initiatives at risk, the deputy defense secretary said today. Story | Special

U.S. Must Consider Sustainability of Afghan Forces

WASHINGTON, Feb. 17, 2011 – The Defense Department has requested enough money to put the Afghan national security forces in a good position to defend their own country, but the current level of funding for the effort is not sustainable in view of budgetary concerns, Defense Secretary Robert M. Gates said here today. Story | Special

SEAL Team Represents All of Military

NEW YORK, May 9, 2011 – The scene at the White House was “tense” during the assault on the compound in Abbottabad, Pakistan, that killed Osama bin Laden, the chairman of the Joint Chiefs of Staff told the audience at the Robin Hood Foundation gala here tonight. Story | Special

Bin Laden Raid Will Help Defeat al-Qaida, Obama Says

WASHINGTON, May 9, 2011 – The death of Osama bin Laden and the unprecedented collection of intelligence material from the raid that killed the terrorist leader will help the United States deal a serious blow to al-Qaida, President Barack Obama said in a “60 Minutes” interview broadcast on CBS last night. Story | Special

Leaders Honor 9/11 Victims at Ground Zero, Pentagon

WASHINGTON, May 5, 2011 – Four days after announcing the killing of al-Qaida leader and 9/11 attack mastermind Osama bin Laden, top administration officials remembered those killed in the attacks with ceremonies today at ground zero in New York City and at the Pentagon here. Story | Special

Survivors Call bin Laden’s Death ‘Bittersweet’

WASHINGTON, May 3, 2011 – When Wendy Duffman first heard that Osama bin Laden, al-Qaida’s leader and the mastermind behind 9/11, was dead, she felt a sense of elation, then relief. Story | Special

Leaders Describe Path to Peace in Libya

WASHINGTON, April 15, 2011 – NATO nations will continue operations against the regime in Libya until Moammar Gadhafi leaves power, the leaders of the United States, Great Britain and France wrote in an article published in their countries today. Story | Special

Secretary: Initial Libya Mission Complete, Successful

WASHINGTON, April 1, 2011 – U.S. aircraft will remain on standby as NATO takes over multilateral operations in Libya and the coalition considers its future role there, Defense Secretary Robert M. Gates told a Senate committee yesterday. Story | Special

Obama Makes Case for U.S. Participation in Libya

WASHINGTON, March 28, 2011 – It was in America’s vital interests to stop a massacre in Libya, President Barack Obama said today at the National Defense University. Story | Special

Forces Accomplish No-fly Zone Mission, Secretary Says

WASHINGTON, March 27, 2011 – U.S. and coalition forces have accomplished the no-fly zone aspect of the United Nations mission in Libya, Defense Secretary Robert M. Gates said during a television interview aired today. Story | Special

Marines Airlift 45 Egyptians Home From Tunisia

WASHINGTON, March 11, 2011 – A Marine Corps KC-130 aircraft has airlifted 45 Egyptians from Djerba, Tunisia, to Cairo in the latest transport of refugees from Libya, Pentagon spokesman Marine Corps Col. Dave Lapan said today. Story | Special

People’s Movements Reject Repressive Ideologies

WASHINGTON, March 11, 2011 – The tremendous change occurring across the Middle East and North Africa provides tremendous opportunities for democracy and demonstrates the rejection of violent, repressive ideologies possessed by al-Qaida and the current Libyan and Iranian regimes, National Security Advisor Tom Donilon said here yesterday. Story | Special

Air Force Transports Refugees Back to Egypt

WASHINGTON, March 9, 2011 – Two U.S. C-130s will transport Egyptian refugees from Tunisia to Cairo today, Defense Department officials said. Story | Special

Captain Cares for Pets Left Behind

WASHINGTON, March 14, 2011 - By Feb. 1, the U.S. Department of State had ordered the departure of dependants and all non-emergency U.S. government personnel and their families from Egypt. But not all "members" of the families departed -- the four-legged ones stayed behind. Story | Special

Cyber Command Builds ‘Cyber Warrior’ Capabilities

FORT MEADE, Md., Sept. 27, 2011 – Recognizing there’s no cookie-cutter formula for a “cyber warrior,” the outgoing chief of staff at U.S. Cyber Command said the strong, diverse capabilities already in place will provide the foundation for the military’s professional cyber corps. Story | Special

DOD Releases First Strategy for Operating in Cyberspace

WASHINGTON, July 14, 2011 – The Defense Department’s first strategy for operating in cyberspace is a milestone in the fight to protect the nation from potentially devastating network attacks, Deputy Defense Secretary William J. Lynn III said today. Story | Special

DOD, Industry Address ‘Intense Challenge’ of Cyber Security

ARLINGTON, Va., Nov. 7, 2011 – Senior Defense Department officials and members of the information technology industry met here today to discuss how to better protect military and commercial cyberspace. Story | Special

Cyber Defense Requires Teamwork, Agility

WASHINGTON, Oct. 27, 2011 – The commander of U.S. Cyber Command called for increased collaboration among the government, industry and America’s allies in developing more defensible networks to confront escalating global cyber threats. Story | Special

DOD Space Program Broadens Industry, Foreign Partnerships

WASHINGTON, July 19, 2011 – The Defense Department is expanding partnerships with spacefaring companies and nations to maintain the strategic advantage it gains in space, the deputy assistant secretary of defense for space policy said today. Story | Special

National Security Space Strategy Targets Safety, Stability

WASHINGTON, Feb. 4, 2011 – The National Security Space Strategy released today responds to the realities of a space environment that is increasingly crowded, challenging and competitive, said senior Defense Department officials. Story | Special

Obama: America Has Emerged Stronger From 9/11

WASHINGTON, Sept. 11, 2011 – President Barack Obama today remembered those who were lost to terrorist attacks a decade ago and said the American commitment to freedom, justice, courage and liberty has not dimmed in the face of many trials. Story | Special

Biden Honors Victims, Families, Service Members

WASHINGTON, Sept. 11, 2011 – Vice President Joe Biden today joined Defense Secretary Leon E. Panetta and Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, at a Pentagon ceremony marking the 10th anniversary of the 9/11 terrorist attacks. Story | Special

Nation Stronger, Safer Since 9/11, Panetta Says

WASHINGTON, Sept. 11, 2011 – As he stood where a hijacked airliner slammed into the Pentagon 10 years ago today, Defense Secretary Leon E. Panetta said the United States has become stronger and safer since Sept. 11, 2001. Story | Special

Camp Leatherneck Commemorates 9/11 Anniversary

WASHINGTON, Sept. 11, 2011 – Of all the events that took place when terrorists attacked the United States 10 years ago, the best memories are those of the heroes who stood up to protect America’s freedom, the commander of Regional Command Southwest said at Camp Leatherneck, Afghanistan, today. Story | Special