The events leading up to the annexation of Texas and the Mexican War were followed by Jay with the closest attention. The injustice and cruelty with which Mexico was treated throughout these proceedings by the United States Government excited his warmest indignation. He was deeply grieved at events which seemed to postpone indefinitely the emancipation of the slaves; his fears were aroused for the security of free institutions in the North by the great impetus given to the Southern spirit of domination. But above all he felt the disgrace incurred by his own country in forcing upon a weak and friendly power a desolating war for the sole object of wresting from it a territory to be peopled by slaves. The result of Jay's minute knowledge of this dark page in American history was embodied in a volume entitled "A Review of the Causes and Consequences of the Mexican War," which was published in 1849. In this searching "Review" Jay exposed the parentage of the movement for the acquisition of Texas in the desire of the South to extend the territory devoted to slavery, with the twofold object of creating a new market for slave-breeders and of giving to the slave States an overwhelming control of Congress. He traced the devious paths of intrigue by which a rebellion was fomented in Texas by Americans settled there for that express purpose; the encouragement and aid given secretly to the rebels by the United States; the recognition of their independence; and finally the subterfuges adopted to achieve the annexation in violation of international rights and the Constitution itself. Jay set forth plainly the fact that hostilities were begun by the United States troops; he described the military operations by which a weak and defenceless people were reduced to consent to a dismemberment of their country; he showed the enormous cost in life and money involved in this war undertaken to furnish a new market for slaves and new power to slaveholders. Jay's "Review of the Mexican War" is a contribution to the history of the country which students cannot afford to pass unread. The views expressed in it are painful to patriotism for the reason that they are dictated by the pure patriotism which would make known the whole truth as a warning to posterity. The book on the Mexican War was written originally for the American Peace Society, which had offered a prize for the best work on the subject. The committee appointed to pass judgment on the dissertations presented in competition awarded the prize to Jay's book on condition that he should expunge from it all "general censures on the Whig party." Jay refused to comply with this condition and the prize went to another. But the Peace Society recognized that the value of Jay's book lay in its impartial character and caused it to be published as the exposition of the society's views.