On Monday, both armies continued in the same position. The Confederates had strengthened some of their works. During the ensuing night, the army evacuated Fredericksburg and retired across the river to its former position. The artillery crossed first, followed by the infantry, the last of whom left about daylight. The pontoon bridges were then removed and all communication cut off. The movement was not perceived by the Confederates until it was too late to do any injury to the retreating force. The following is the despatch of General Burnside announcing this movement: HEADQUARTERS ARMY POTOMAC, } SIX O’CLOCK, P. M., _December 16, 1862_. } Major-General HALLECK: The army was withdrawn to this side of the river because I felt the position in front could not be carried, and it was a military necessity either to attack or retire. A repulse would have been disastrous to us. The army was withdrawn at night, without the knowledge of the enemy, and without loss either of property or men. A. E. BURNSIDE, Major-General Commanding. The Federal loss was as follows: General Sumner’s division on the right, killed, four hundred and seventy-three; wounded, four thousand and ninety; missing, seven hundred and forty-eight. Total, five thousand three hundred and eleven. General Hooker’s division on the centre, killed, three hundred and twenty-six; wounded, two thousand four hundred and sixty-eight; missing, seven hundred and fifty-four. Total, three thousand five hundred and forty-eight. General Franklin’s division on the left, killed, three hundred and thirty-nine; wounded, two thousand five hundred and forty-seven; missing, five hundred and seventy-six. Total, three thousand four hundred and sixty-two. Grand total, killed, one thousand one hundred and thirty-eight; wounded, nine thousand one hundred and five; missing, two thousand and seventy-eight. Total, twelve thousand three hundred and twenty-one. The Confederate loss was comparatively small, having been sheltered by their works. General Burnside in his report to the general-in-chief, thus explains his defeat: