The offensive began with a westward move on January 20, 1863, in unseasonably mild weather. Burnside, with a head start, altered his plan to aim at Banks' Ford, a closer, quicker crossing. At dawn of January 21, engineers would push five bridges across; after that, two grand divisions would be over the river in four hours. Meanwhile, another grand division would distract the Confederate troops by repeating the December crossing at Fredericksburg. During the night of the 20th, the rain began, and by the morning of the 21st, the earth was soaked and the river banks had the appearance of a quagmire. Already, fifteen pontoons were on the river, nearly spanning it, and five more were amply sufficient. Burnside began at once to bring up his artillery, which had the effect of making a perfect mortar bed. For a considerable area around the ford all day the men worked in the rain but to little purpose. Quite a number of cannon were advanced near the ford, but the 22nd only added to the storm, and the artillery, caissons and even wagons were swamped in the mud.