Why can out military not defend itself inside the US

There have been two successful attacks that against US Army installations in the last few years. This brings my to my point why can soldiers not defend themselves outside of a war zone? The soldiers at Ft. Hood were out processing to go to Afghanistan yet there was not a loaded weapon in the place except for a civilian police officer. In Little Rock the same thing was in place the young men just back from boot camp were not armed and neither were any of the recruiters.

If there is a segment of our society that I would expect to be armed it would be our armed forces. Yet the military is making it harder for them to be that way at home. Yes there is a law about the armed forces carrying out operations inside of the US. There is no law however that should leave them defenseless in case of an attack.