Its not because of mail bombs it is to confront a caravan of potential immigrants walking from Guatemala and will arrive at the border perhaps this year or next.

800 crack troops fresh from Afghanistan will spend the holidays waiting at he border with plans for 1,900 National Guard in reserve.
The last time we brought troops to the border only one suspicious person was shot and killed. An 18 year old American goat herder on American soil.

I do not know if we used troops to help with our last Hurricane but I doubt it. As national emergency declarations go, Irene Wilson from Tennessee is one who says she feels much safer now.