The enemy moved up in force last evening about seven o'clock, in a shower of rain, to attack. I opened on them from the position which the troops occupy above the town, and from the Dahlgren battery on the mountains. The enemy then retired. Their pickets attacked ours twice last night within 300 yards of our works. A volley from General Slough's breastworks drove them back. We lost one man killed. Enemy had signal-lights on the mountains in every direction. Their system of night-signals seems to be perfect. They fire on our pickets in every case. My men are overworked. Stood by their guns all night in the rain. What has become of Generals Fremont and McDowell? R. SAXTON. HON. E. M. STANTON, _Secretary of War_. At Williamsport on the Maryland side, twelve miles above, General Banks likewise sent a telegram to the Government at Washington. WILLIAMSPORT, May 28, 1862. Have received information to-day which I think should be transmitted, but not published over my name, as I do not credit it altogether. A merchant from Martinsburg, well known, came to inform me that in a confidential conversation with a very prominent secessionist, also merchant of that town, he was informed that the policy of the South was changed; that they would abandon Richmond, Virginia, everything South, and invade Maryland and Washington; that every Union soldier would be driven out of the Valley immediately. This was on Friday evening, the night of attack on Front Royal. Names are given me, and the party talking one who might know the rebel plans. A prisoner was captured near Martinsburg to-day. He told the truth I am satisfied, as far as he pretended to know. He was in the fight at Front Royal and passed through Winchester two hours after our engagement. He says the rebel force was very large--not less than twenty-five thousand at Winchester and 6000 or 7000 at Front Royal; that the idea was general among the men that they were to invade Maryland. He passed Ashby yesterday, who had twenty-eight companies of cavalry under his command; was returning from Martinsburg, and moving under orders, his men said, to Berryville. There were 2000 rebels at Martinsburg when he passed that town yesterday. These reports came to me at the same time I received General Saxton's dispatch and the statement from my own officer that 4000 rebels were near Falling Waters, in my front. N. P. BANKS, _Major-General Commanding._ HON. E. M. STANTON.