Florida ? Defense Secretary Robert Gates on Friday welcomed David Petraeus as the new chief of Central Command with responsibility for America’s two wars, saying he hopes the general will help bring needed coherence to the U.S. and allied strategy in an increasingly volatile Afghanistan.

Gates presided at Petraeus’ change-of-command ceremony at Central Command headquarters in Tampa, Fla. He later told reporters traveling with him to Jacksonville that Petraeus faces many new challenges after winning wide praise for rescuing a failing Iraq war strategy.

Petraeus spent 20 months as the top U.S. commander in Baghdad. Now he will oversee U.S. military operations across the Middle East – from Egypt to the Persian Gulf – as well as Afghanistan and Pakistan.