In the absence of formal notification of administration intentions, Young and other Mormon leaders interpreted the army's coming as religious persecution and adopted a defensive posture. Under his authority as governor, Young declared martial law and deployed the local militia, the Nauvoo Legion, to delay the troops. Harassing actions included burning three supply trains and driving hundreds of government cattle to the Great Salt Lake Valley. The "scorched earth" tactics forced Albert Sidney Johnston's Utah Expedition and the accompanying civil officials to improvise winter quarters (at Camp Scott and Eckelsville), near Burned-out Fort Bridger, while the nation feared the worst.

During the winter both sides strengthened their forces. Congress, over almost unanimous Republican opposition, authorized two new volunteer regiments, and Buchanan, Secretary of War John B. Floyd, and Army Chief of Staff Winfield Scott assigned 3,000 additional regular troops to reinforce the Utah Expedition. Meanwhile, the Mormon communities were called upon to equip a thousand men for duty in the one hundred miles of mountains that separated Camp Scott and Great Salt Lake City.