That is the message. Fitz-John Porter has twelve thousand troops. They have been spectators of the battle through the day. They have had breakfast and dinner, and nearly two days of rest since their arrival upon the ground. They might be a thunderbolt at this moment. Couch's and Humphrey's divisions will be up during the night. But they are the only reserves present. Slocum has taken Sedgwick's place. He has not been engaged, and his men stand with ordered arms. Shall Porter be put in? McClellan consults Porter and Sykes, and then replies:-- "Tell General Burnside that I will send him Miller's battery. I have no infantry to spare. He must hold his ground till dark. Tell him if he cannot hold his ground, he may fall back to the bridge; but he must hold that, or all is lost." Porter's corps and Slocum's division of Franklin's, eighteen thousand men in all, have taken no part in the battle. Smith is holding an important position. He has made one gallant charge, but his troops are ready to fight. There are twenty thousand men which can take the offensive, and nearly a hundred guns of the artillery.[76] [Footnote 76: See McClellan's statement of the number of troops present, p. 214, Report.] The right flank of the Rebels is all but turned. Wilcox is close upon the town. Rodman has driven Hill, and is holding his ground. Such is the condition of affairs as the sun goes down. It is useless for Burnside to struggle without supports. He fights till the coming on of twilight, and then recalls his troops. The regiments of Fairchild's brigade, far up on the hillside, upon ground won from the enemy by their valor, go back reluctantly. "The men," says Lieutenant-Colonel Kimball, of the Ninth New York, "retired in good order, at a slow step, and with tears in their eyes, at the necessity which compelled them to leave the field they had so dearly won."[77] [Footnote 77: Lieutenant-Colonel Kimball's Report.] It was a necessity. Without reinforcements he could not hold his ground, and Lee could cut him off if he remained so far from the bridge. The daylight is dying out. Through the hours from early morning the roar of battle has been unceasing. Four hundred cannon have shaken the earth, and nearly two hundred thousand men have struggled for the mastery. At times the storm has lulled a little, like the wind at night, then rising again to the fierceness of a tornado. In the intervals of the cannonade, low moans come up from the hollows, like the wail of the night-wind on a lonely shore.