Lieutenant Hood was in command of the personal mounted escort of Lieutenant R.S.Williamson, who was charged with the duty of making such explorations and surveys as would determine the practicability of connecting, by railroad, the Sacramento Valley in California with the Columbia River in Oregon Territory, either through the Willamette Valley, or (if this route should prove to be impracticable) by the valley of the Des Chutes River near the foot-slopes of the Cascade chain.

The survey was being made in accordance with an act of Congress, which provided both for ascertaining the must practicable and economical route for a railroad between the Mississippi River and the Pacific Ocean, and for military and geographical surveys west of the Mississippi River.
Fort Reading was the starting-point for this exploring expedition, and there I arrived some four or five days after the party under Lieutenant Williamson had begun its march.

His personal escort numbered about sixty mounted men, made up of detachments from companies of the First Dragoons, under command of Lieutenant Hood, together with about one hundred men belonging to the Fourth Infantry and Third Artillery, commanded by Lieutenant Horatio Gates Gibson, the present colonel of the Third United States Artillery.

Lieutenant George Crook--now major-general--was the quartermaster and commissary of subsistence of the expedition.
The commanding officer at Fort Reading seemed reluctant to let me go on to relieve Lieutenant Hood, as the country to be passed over was infested by the Pit River Indians, known to be hostile to white people and especially to small parties.

I was very anxious to proceed, however, and willing to take the chances; so, consent being finally obtained, I started with a corporal and two mounted men, through a wild and uninhabited region, to overtake if possible Lieutenant Williamson.