The Secretary of Defense isn't better informed than the Joint Chiefs of Staff, who back Obama's reduction plans.
the JCS follow orders - as members of the military, their ability to speak publicly is sharply curtailed. that the SecDef spoke out at all is amazing, and probably testament mostly to his long experience and the ability to operate independently of his boss. he's been here before, he will be around later, etc.
I am asking what specific reduction, IYO, causes what specific danger, cpwill.
Ships have training and refit schedules, just like units do. So, for example, when we say that we are reducing from 11 Carrier groups to 9 or 8, we aren't
really going down to 9 or 8 in the sense that that is our combat power. We are going down to however many of that 9 or 8 we can maintain forward.
Let's put them on a full pedal to the metal speed, assume that nothing on ships ever break, and say that we are going to manage a 1-for-1 swap; meaning that crews will be home six months and gone six months and home six months and gone six months. This is the deployment cycle that both the Army and the Marines have said in Afghanistan/Iraq will destroy a unit and eventually a service, but we will give the Navy the benefit of the doubt and assume they are all Iron Men.
That means at any given time there are 4 carrier groups afloat. Now, you need two to provide credible threat to the Iranians, a third in the area of the malacca straights, a fourth in the Med to respond to any scenario in Libya or Syria (here's a fun one: Syria has chemical weapons stores. Al Qaeda is in the opposition. What happens when Al Qaeda captures a chemical weapons store?), and a fifth in the Pacific. So that's five carrier groups that you need out of the four that you have - and that's
before an earthquake hits Japan sparking a nuclear crisis, a tsunami overruns Indonesia, flooding wipes out half of Pakistan, the North Koreans start shelling the South Koreans, a Haitian earthquake knocks over all ten of that nations finished structures, Somali Pirates threaten take hostages and threaten to choke the oil trade.... etc. so on and so forth.
The US Navy is the single most important branch of service that we have to maintain if we wish to retain the ability to engage in global trade and avoid regional conflagration in the Middle East and Chinese hegemony in the Pacific. The vast majority of humanity doesn't live on temperate zone plains perfect for tanks; it lives in the littorals.