The rescue of the prisoners of war on the 15th ultimo caused great excitement among the enemy, and tended very much to disorganize their forces, and the important arrival of the reinforcements to my command determined me to take the field as soon as possible; accordingly, I left this place on the morning of the 26th instant with two hundred and seventeen officers and men; Lieutenant Halleck, United States engineers, acting chief of staff, and Passed Midshipman Duncan, United States navy, temporarily attached to the mounted portion of Captain Naglee's command. The afternoon of the 27th, a party of fifteen men captured, in San Antonio, Pineda, the commander of the Mexican forces, with his secretary, Serrano. The morning of the 29th, having received information that the enemy had concentrated their forces in Todos Santos, we pressed on with all speed, fearing they might evade us, by retreating towards Magdalena Bay. The morning of the 30th, about ten o'clock, having received accurate information respecting the enemy, Captain Naglee with forty-five mounted men was despatched to intercept the road leading from Todos Santos to Magdalena Bay, and, if practicable, to attack the enemy in the rear at the same time our main body made its attack in front. The road leading from Todos Santos to La Paz, for some distance before reaching the first named place, passes through a dense growth of chaparral, (very favorable for an ambush), and in this the enemy made their arrangements to receive us. We left the road about five miles from Todos Santos and marched along a ridge of high land on the north side of the river, having full view of the enemy's operations. They then took possession of a commanding hill directly in our route, between three and four miles from Todos Santos, with their Indians in front. Companies A and B, under the direction of Lieutenant Halleck, were deployed as skirmishers in such a manner as to expose the enemy to a cross-fire. The enemy opened their fire at long distance, but our force advanced steadily, reserving their fire until within good musket range, when it was delivered with great effect, and the enemy retreated very rapidly, after a short but sharp engagement. At this time, Captain Naglee being near Todos Santos, and hearing the firing, attacked the enemy in rear, and after a severe action completed their dispersion. Our men and horses being too much fatigued by their long march to pursue the scattered enemy, we marched on to Todos Santos. The loss of the enemy in this engagement cannot be ascertained with any accuracy; we know of ten killed and eight wounded. Our loss was nothing; one man and the horse of Acting Lieutenant Scott were slightly wounded, the enemy, as usual, firing too high. Our officers and men fully sustained the character they won on the 16th and 27th of November last.