>"An envoy of the United States repaired to Mexico with full powers to adjust every existing difference. But though present on Mexican soil by agreement between the two Governments, invested with full powers, and bearing evidence of the most friendly dispositions, his mission has been unavailing. The Mexican Government not only refused to receive him or listen to his propositions, but after a long-continued series of menaces have at last invaded our territory and shed the blood of our fellow-citizens on our own soil."
>"Five days after the date of Mr. Slidell's note General Herrera yielded the Government to General Paredes without a struggle, and on the 30th of December resigned the Presidency. This revolution was accomplished solely by the army, the people having taken little part in the contest; and thus the supreme power in Mexico passed into the hands of a military leader."
>"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."
>"As war exists, and, notwithstanding all our efforts to avoid it, exists by the act of Mexico herself, we are called upon by every consideration of duty and patriotism to vindicate with decision the honor, the rights, and the interests of our country."
This wasn't a land grab, you killed Americans on our own soil and had been doing this for over two decades. This was a war you started and a war we finished.
And what is happening today? Mexicans killing Americans and acting like this land is theirs. I think we need a Mexican-American War II.
http://www.dmwv.org/mexwar/documents/polk.htm