An incident at the very outset of his career in the Senate, betrayed some little lack of self-restraint.  When Senator Cass introduced the so-called Ten Regiments bill, Calhoun asked that its consideration might be postponed, in order to give him opportunity to discuss resolutions on the prospective annexation of Mexico.  Cass was disposed to yield for courtesy’s sake; but Douglas resented the interruption.  He failed to see why public business should be suspended in order to discuss abstract propositions.  He believed that this doctrine of courtesy was being carried to great lengths.[241] Evidently the young Senator, fresh from the brisk atmosphere of the House, was restive under the conventional restraints of the more sedate Senate.  He had not yet become acclimated.

Douglas made his first formal speech in the Senate on February 1, 1848.  Despite his disclaimers, he had evidently made careful preparation, for his desk was strewn with books and he referred frequently to his authorities.  The Ten Regiments bill was known to be a measure of the administration; and for this reason, if for no other, it was bitterly opposed.  The time seemed opportune for a vindication of the President’s policy.  Douglas indignantly repelled the charge that the war had from the outset been a war of conquest.  “It is a war of self-defense, forced upon us by our enemy, and prosecuted on our part in vindication of our honor, and the integrity of our territory.  The enemy invaded our territory, and we repelled the invasion, and demanded satisfaction for all our grievances.  In order to compel Mexico to do us justice, it was necessary to follow her retreating armies into her territory ... and inasmuch as it was certain that she was unable to make indemnity in money, we must necessarily take it in land.  Conquest was not the motive for the prosecution of the war; satisfaction, indemnity, security, was the motive—­conquest and territory the means."[242]

Once again Douglas reviewed the origin of the war re-arguing the case for the administration.  If the arguments employed were now well-worn, they were repeated with an incisiveness that took away much of their staleness.  This speech must be understood as complementary to that which he had made in the House at the opening of hostilities.  But he had not changed his point of view, nor moderated his contentions.  Time seemed to have served only to make him surer of his evidence.  Douglas exhibited throughout his most conspicuous excellencies and his most glaring defects.  From first to last he was an attorney, making the best possible defense of his client.  Nothing could excel his adroit selection of evidence, and his disposition and massing of telling testimony.  Form and presentation were admirably calculated to disarm and convince.  It goes without saying that Douglas’s mental attitude was the opposite of the scientific and historic spirit.  Having a proposition to establish, he cared only for pertinent evidence.  He rarely inquired into the character of the authorities from which he culled his data.