NEW YORK (Reuters) - Former Defense Secretary Robert Gates will pen two forthcoming books -- firstly a memoir expected to be released in 2013 and another about his philosophy on leadership, his publisher said on Tuesday.

Gates, 67, departed as Pentagon chief in June after four and a half years serving under former President George W. Bush and then Barack Obama. He took over the position from Donald Rumsfeld who resigned amid criticism over his handling of the Iraq war.

The memoir will look at the key events during Gates' tenure, including U.S. strategy in Afghanistan, the withdrawal of troops in Iraq and the Obama administration's repeal of the "Don't Ask, Don't Tell" laws that prevented gay and lesbians in the military from serving openly, publisher Alfred A. Knopf said.

"I want to tell my story of constant conflict abroad and in Washington. I will share insights gleaned from my experience of working for two very different presidents in two administrations of very different political stripes," Gates said in a statement.

It will also include Gates' decision to replace the top commander in Afghanistan Gen. David D. McKiernan after just one year on the job with Gen. Stanley A. McChrystal.

McChrystal was eventually fired by Obama for remarks he made to Rolling Stone magazine that disparaged the president and other civilian leaders and replaced with Gen. David Petraeus.

Gates, a former CIA entry-level officer who rose to serve as Director of Central Intelligence, will pen a second book that will focus on leadership philosophy and his views on great leaders and "how to successfully reform and change public institutions," Gates said in the statement.

He added: "At a time when government at every level seems paralyzed by bureaucracy and politics, I want to share how I overcame those obstacles and enabled dedicated professionals to better accomplish their missions -- techniques I believe also apply to most organizations and companies."

(Reporting by Christine Kearney, editing by Jill Serjeant)