by dispatching Rupert and 7,000 cavalry in a flying column to disrupt and harass the Parliamentary retreat. Encountering Essex's forces at Aldbourne Chase, Rupert made battle; however, lacking enough troops to engage the Parliamentarians directly, he instead attacked a section of their army, causing chaos and crucially delaying Essex's march just enough for Charles's forces to close the gap. The effect of Rupert's actions, even after his forces disengaged, was to force another delay in the Parliamentarian retreat; Essex spent much of 19 September looking after wounded soldiers and, when he finally managed to begin moving again, he was confronted with swampland and bog which further delayed him while the Royalists marched across the relatively open chalk downs above the Kennet. These hardships meant that the Royalists arrived at Newbury before Essex, with both armies settling down for the night outside the town, too exhausted to immediately fight. Newbury Landscape The landscape of the area around Newbury was a significant factor in the tactics of both sides during the resulting battle. Though the land was mostly open country, a crescent-shaped escarpment known as Biggs Hill sat between the Royalist and Parliamentarian forces. To either side of Essex's army lay open fields, while the battlefield was bracketed by the River Kennet on one side and the River Enborne on the other, which neither side attempted to cross on foot. Essex's most obvious route of advance was to push past the Royalist forces, secure the bridge and return to London. Unfortunately, the open area approaching the bridge was a "killing ground"; soldiers would be entirely in the open and forced to march no more than six abreast, which would prevent Essex effectively deploying against a Royalist attack and leave the Parliamentarian's forces bunched up and subject to artillery fire. Even if Essex managed to cross the bridge, the other side of the river featured several hundred metres of waterlogged ground, which would slow his soldiers and leave them open to attack while necessitating the abandonment of the Parliamentarian artillery, a "major humiliation for a seventeenth-century army". The only alternative to a bridge-based retreat would be to bypass Newbury completely by marching around the Royalists, but this would again involve moving through open fields and subjecting Essex's soldiers to the attacks of Royalist cavalry, who were described as greatly outnumbering the Parliamentarian cavalry. Confronting the Royalists directly would involve moving into ground described