The main assaults by ever-increasing formations of Luftwaffe bombers, escorted by Bf109s and Bf110s, were initially aimed at British merchant shipping convoys plying their trade of coal and other materials from the north of England to the southern ports. These attacks by the Germans often met with increasing success although RAF Spitfires and Hurricanes endeavoured to repel the Heinkels, Dorniers and Ju88s, frequently with ill-afforded loss in pilots and aircraft.
Within a month the Channel was effectively closed to British shipping. Only a change in the Luftwaffe’s tactics in mid-August, when the main attack changed to the attempted destruction of the RAF’s southern airfields, allowed small convoys to resume sneaking through without too greater hindrance.