Floyd Rumin reports in Counterpunch of the 1930s contingency plans to invade just about anybody (should it become necessary). He compares those old plans to invade Mexico with the planing of the Iraq invasion:
In both plans, the goal is to seize control of another nation’s oil.
In both plans, there is a priority on protecting the oil production facilities from damage by the defending national forces.
In both plans, economic sanctions and blockade will weaken the nation prior to the U.S. invasion.
In both plans, Congressional authorization for war can be circumvented by presidential command and by twisting of words.