Up to May 24th, the Union troops had been kept strictly on the Washington side of the Potomac. On that date, Gen. Joseph K. F. Mansfield sent three columns of troops across the river into Virginia, to drive back the Confederate pickets which were within sight of the capital. From Washington to Alexandria, a few miles down the river, a line of fortifications was established, which, with the approaches to Washington from Maryland in Union control, seemed to assure the safety of the city. Troops from all the loyal States had continued to arrive at Washington. The ninety thousand men who had responded to the first call of the President had enlisted for three months. While these troops predominated in the service it was not the expectation of General Scott to undertake any serious operations. He proposed to utilize these for the defence of Washington; the garrisoning of Fortress Monroe, with possibly the recovery of the Norfolk Navy Yard; the reinforcement of Patterson at Harper's Ferry and of McClellan in the Shenandoah; and the control of the border States. When the half million of three-years men called out in May and July should be equipped with the half billion of dollars voted by Congress, and instructed and drilled during a summer encampment, larger military operations were to ensue; but not before. But after the mishap to Butler's men at Big Bethel, and the ambushing of a troop train at Vienna, near Washington, there was a public demand for some kind of vigorous action which should retrieve the national honor, tarnished and unavenged since Sumter, and should justify the military establishment, which to the non-military mind seemed already enormous. Brigadiers and gold lace and regiments playing "high jinks" in their camps convenient to the attractions of Washington became a by-word, and "On to Richmond!" became the cry of those who wanted to see some fighting, now there was an army, and wanted to see secession rebuked and rebellion nipped in the bud. Under the stimulus of this public demand, which, however erroneous from a military point of view, could not be ignored, a forward movement was decided on.