The Belgian forces in Antwerp conducted three sorties in late September and early October, which interrupted German plans to send troops to France, where reinforcements were needed to counter the French armies and the British Expeditionary Force (BEF). A German bombardment of the Belgian fortifications with heavy and super-heavy artillery began on 28 September. The Belgian garrison had no hope of victory without relief and despite the arrival of the Royal Naval Division beginning on 3 October the Germans penetrated the outer ring of forts. When the German advance began to compress a corridor from the west of the city along the Dutch border to the coast, through which the Belgians at Antwerp had maintained contact with the rest of unoccupied Belgium, the Belgian Field Army commenced a withdrawal westwards towards the coast.