During this period, on the 24th of April, 1861, he was married to Miss Sarah Lyon, a young lady of New York, who was famous for the loveliness of her person and character, whom he had first met two years before.  It was on a short wedding trip to his native state that he offered his services to the Governor.  The latter had already raised and organized two regiments of infantry but without hesitation he promised Captain Smith the next, as soon as it should be called for.

Meanwhile he was still subject to duty as an engineer officer, and as such, strangely enough was ordered to report to Major General Benjamin F. Butler, fresh from the life of a successful lawyer, then in command at Fortress Monroe, where he arrived on the 1st of June, 1861.  While there he conducted several important reconnaissances in the direction of Yorktown and Big Bethel, and thus became acquainted with a region in which he was afterwards to play a most important part.  His services lasted something less than two months, and became still more notable from the fact that they made him thoroughly acquainted with General Butler.  They were brought suddenly to an end by the reappearance of his old trouble, which in time made it necessary for him to take a sick-leave.  The surgeon who had him in charge directed him to again seek the tonic climate of Brattleborough in his native State.  According to promise, his good friend, the Governor, took the earliest opportunity to send him his commission as Colonel of the Third Regiment of Vermont Volunteer Infantry, to date from July 16th.  But owing to the scarcity of regular officers, he had previously been ordered to duty on the staff of General McDowell, then commanding the army in front of Washington, though, his health did not permit him to join in time to take part in the forward movement which ended in the disastrous battle of Bull Run.

As soon however as his strength was sufficiently re-established Colonel Smith repaired to Washington, and in the rush and excitement which prevailed after the return of the defeated army to that neighborhood, he was engaged in helping to fortify and defend that city till the danger was past and the requirements of his regiment made it necessary for him to take command and begin its preparation for active service.  It is to be noted that there was an unaccountable reluctance on the part of the War Department at the time, to permit the detachment of officers belonging to the various staff corps, for the purpose of commanding volunteers, but this was overcome without much difficulty in his case, and he began his career as an infantry colonel opportunely at the very time that McClellan was re-organizing the defeated army and badly needed the assistance of educated officers.  Deeply impressed with the importance of stimulating the pride of the volunteers, and of keeping alive the heroic traditions of their state by all proper means, Colonel Smith recommended that the Vermont regiments should be brigaded