Lee realized that a knoll in front of his lines would give the British, now deployed from column into line formation, command of the ground and render his position untenable. With no knowledge of the main body's whereabouts and believing he had little choice, Lee decided to fall back farther, across the Spotswood Middle Brook bridge. He believed he would be able to hold the British there from Perrine's Hill until the main body came up in support. With his aides out of action, Lee pressed whomever he could find into service as messengers to organize the withdrawal. It was during this period that he sent the army auditor, Major John Clark, to Washington with news of the retreat. But Washington was by now aware, having learned from Lee's troops who had already crossed the ravine.