War!

The United States Congress declared war on Mexico on this date in 1846. (Open hostilities had begun in April.)

Two days earlier, in a message to Congress, President Polk had claimed:

The cup of forbearance had been exhausted even before the recent information from the frontier of the Del Norte [Rio Grande]. But now, after reiterated menaces, Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American soil. She has proclaimed that hostilities have commenced, and that the two nations are now at war.

(Of course, Mexico did not recognize the Rio Grande as the border.)

Within a few hours the House passed a resolution authorizing war 173-14. The Senate interrupted its debate about whether to abolish West Point and discussed the matter of war for a day before agreeing 42-2.

At a cabinet meeting on the 13th, Polk corrected Secretary of State Buchanan of the notion that the U.S. did not intend to acquire New Mexico or California. Such acquisition might be necessary to indemnify us Polk said, and he would accept war with “either England or France or all the Powers of Christendom” rather than pledge “that we would not if we could fairly and honourably acquire California or any other part of Mexican territory which we desired.”