Events in history have no actual beginning. One can start to explain an event at any point that led up to the event. This is true of the Arizona Bill. Today, for example may be one of the origins of evenets that led to the situation that led to the bill. May 13, 1846 Pres. Polk ordered General Zachary Taylor to seize disputed Texan land. Congress declared war on Mexico, despite protestations by the Mexican government that Thornton had crossed the border into Mexican Texas — a border that Mexico claimed began south of the Nueces River, and which the United States claimed began further to the south at the Rio Grande (Río Bravo). General Mariano Parades seized power in Mexico City, declared his intention of driving the Americans out of Texas, mobilized the Mexican army and ordered an attack on American troops along the Rio Grande. On April 23, 1846 he issued a Declaration of War against the United States. The U. S. did not declare war on Mexico until May 13, after Mexican forces had attacked an American patrol north of the Rio Grande. In the evolution of Presidential power, this day saw the transition of power to declare war. The framers specifically reserved the power to declare war to the Legislative branch, even though chief executives had routinely defended American interests abroad with military means as early as Jefferson’s actions against the Barbary pirates in 1801, but Polk almost demanded that Congress recognize that a state of war already existed, and any who failed to respond would be branded as cowards.