On this date, May 25th of 1862, Stonewall Jackson accomplished a major victory in his Peninsula Campaign by routing the Union forces of General Banks in the First Battle of Winchester, VA.
In consequence of the victory on the 23rdat Front Royal, along with news of Jackson’s multiple advances upon him, General Banks moved his forces down the Shenandoah Valley (to the north) toward Winchester. Harassed along the way at Middletown and Newtown (Stephen’s City), Banks deployed at Winchester to halt the advance. Many Union troops and supplies were captured in this retreat through the valley, to the extent that Banks gained the nickname “Commissary Banks.”

Credit: Map by Hal Jespersen, http://www.posix.com/CW
Jackson’s total command outnumbered Banks by 16,000 to 6,500. The Union center and right lines collapsed under the weight of it all, with troops pulling back through Winchester to Martinsburg … ultimately crossing the Potomac into my current town of Williamsport, MD.
The consequence again of Jackson’s action was to cause a withholding of Union forces from joining McClellan on the Peninsula – as Little Mac was now closing very near to Richmond.
Illustrative of this is a series of telegrams I’ll include here in what I trust is an instructive manner:
On May 24, 1862, President Lincoln wired General McClellan: “In consequence of Gen. Banks’ critical position I have been compelled to suspend Gen. McDowell’s movement to join you. The enemy are making a desperate push upon Harper’s Ferry, and we are trying to throw Fremont’s force & part of McDowell’s in their rear.” McDowell’s 40,000-man force was in the Fredericksburg area, and half of it would be sent away to the west and northwest.
Here is the May 24th telegram to McDowell: “General Fremont has been ordered by telegraph to move from Franklin on Harrisonburg to relieve General Banks, and capture or destroy Jackson’s and Ewell’s forces. You are instructed, laying aside for the present the movement on Richmond, to put 20,000 men in motion at once for the Shenandoah, moving on the line or in advance of the line of the Manassas Gap railroad. Your object will be to capture the forces of Jackson and Ewell, either in co-operation with General Fremont, or, in case want of supplies or of transportation, interferes with his movements, it is believed that the force which you move will be sufficient to accomplish this object alone. The information thus far received here makes it probable that if the enemy operate actively against General Banks, you will not be able to count upon much assistance from him, but may even have to release him. Reports received this moment are that Banks is fighting with Ewell eight miles from Winchester.” … A. LINCOLN.
Here is a 2:00 telegram on May 25th from Lincoln to McClellan: “The enemy is moving north in sufficient force to drive General Banks before him-precisely in what force we cannot tell. He is also threatening Leesburg, and Geary, in the Manassas Gap Railroad, from both north and south – in precisely what force we cannot tell. I think the movement is a general and concerted one, such as would not be if he was acting upon the purpose of a very desperate defense of Richmond. I think the time is near when you must either attack Richmond or give up the job and come to the defense of Washington. Let me hear from you instantly.” A. LINCOLN, President.
And finally, in reply, this is the May 25th immediate response from McClellan to Lincoln: “Telegram received. Independently of it, the time is very near when I shall attack Richmond. The object of the movement is probably to prevent re-enforcements being sent to me. All the information obtained from balloons, deserters, prisoners, and contrabands agrees in the statement that the mass of the rebel troops are still in the immediate vicinity of Richmond, ready to defend it. I have no knowledge of Banks’ position and force now what there is at Manassas; therefore cannot form a definite opinion as to the force against him. I have two corps across Chickahominy, within 6 miles of Richmond; the others on this side at other crossing within same distance, and ready to cross when bridges are completed.”