The first shots were exchanged around 08:00 in an entirely American skirmish between a small detachment of Rangers and Dickinson's militia. Grayson arrived just in time to deploy his troops in support of the militia near a bridge over a ravine and watch the Rangers withdraw. The bridge was on the Englishtown–Monmouth Court House road and spanned the Spotswood Middle Brook, one of three ravines bordered by marshy wetlands or 'morasses' that cut through what would soon become a battlefield. Other than by bridge, the ravines were negotiable with difficulty by infantry and not at all by artillery; any unit cut off on the wrong side or pinned up against them would find itself in grave danger. When Lee caught up with Grayson shortly after the skirmish, Dickinson, who still believed the British occupied Monmouth Court House in force, strongly urged him not to venture across the brook. With intelligence about British activity still contradictory, Lee lost an hour at the bridge. He did not advance until Lafayette arrived with the rest of the vanguard.