a lack of quality in the escort groups. There was very little reserve force that could be sent to augment convoy battles and vessels delayed their refit schedules, making those ships out on escort less capable. Operational history Initially, the NEF was composed of fifteen Royal Navy warships; seven destroyers, four sloops and four corvettes, and twenty-three Royal Canadian warships; six destroyers and seventeen corvettes. NEF's first convoy operation began on 2 June 1941. The first significant convoy battle erupted around convoy HX 133. Six merchant vessels were lost in exchange for two U-boats sunk by British reinforcements to the convoy escort. In August, United States Navy escorts began escort fast convoys (ON and HX designations) between North America and Iceland under the Argentia Agreement. The NEF was restricted to escorting slow convoys (SC and ONS designations). Following the introduction of the US destroyers, German tactics changed, moving concentrations of U-boats around the Atlantic in response to battle and circumstance. In September the U-boats shifted north and encountered convoy SC 42. Escorted by one of NEF's groups and heavily augmented during the ensuing battle, it became the worst loss of the period by Allied escorts with 15 merchant vessels sunk. During the battle, the Canadian escorts were able to sink one U-boat . Following the SC 42 loss, the British requested that the NEF increase the number of escorts per group to six. The NEF was capable of doing so only because of the American escort of HX convoys. In September and October, the Germans began targeting SC convoys at the same time as the Mid-Ocean Meeting Point was moved five degrees further east in order to free British warships for escort duties in other theatres. In October, the NEF was removed as a subordinate unit of Western Approaches Command and placed under the supervision of an American commander, even though the United States was still officially neutral. This decision soon began to affect NEF's capability to operate. In October, Royal Canadian Navy vessels were averaging 28 out of every 31 days at sea. Both US and British concerns over the force's effectiveness became apparent that month. To ease the strain in mid-October, every ocean-going escort of the Royal Canadian Navy was deployed to the NEF. The area of sea which became known as the "Black Pit" coincided with the gap between land-based air cover. This area, coupled with the