The Administration is replacing the chairman of the Joint Chiefs of Staff. Under normal circumstances this would be a ho-hum news item. We need to remember, however, that the neo-cons nightly pray for war with Iran. Also, earlier this year several generals flat out told Bush that if he ordered them to bomb Iran they would resign in protest.
Let us ignore Defense Secretary Gates public reasons for replacing the nation's top generals (Public reasons are almost always public lies). Let us look, instead at a more likely reason. Chairman of the Joint Chiefs General Peter Pace has publically stated that the United States has "zero intent" to attack Iran. If Bush's intent is war with Iran, one of his first steps would have to be removing General Pace from his office.
There is no evidence that the proposed replacement, Admiral Michael Mullen, is a hothead. He too has stated there are no plans to attack Iran. Still, it is incumbant upon the United States Senate to insure that Admiral Mullen will refuse to follow any orders to attack Iran or any other sovereign nation without the constitutionally mandated approval of both houses of the United States Congress.
See also Seymour Hersh from last year.
UPDATE: The real news is who is being nominated for vice-chairman. Marine General James Cartwright is currently head of the U.S. Strategic Command. Cartwright has been far more sanguine towards war with Iran. His appointment to head STRATCOM in 2004 was considered strange at the time because the post usually goes to an Air Force or Navy commander. As a Marine, Cartwright had little experience in strategic bombardment. But, as a Marine, Cartwright is a gung-ho, never met a war he didn't like, soldier. Cartwright has driven a space-based weapons program and a plan for America to wage world war with the chilling code name, Global Strike. With Cartwright on the Joint Chiefs of Staff war with Iran becomes much more likely and the use of American nuclear weapons in the event of such a war becomes a near certainty.
See also: two Jorge Hirsch articles , , Frances Mendenhall, and Dan Plesch