The Liberators made a significant contribution to Allied victory in the Battle of the Atlantic against German U-boats. Aircraft had the ability to undertake surprise air attacks against surfaced submarines. Liberators assigned to the RAF's Coastal Command in 1941, offensively to patrol against submarines in the eastern Atlantic Ocean, produced immediate results. The introduction of Very Long Range (VLR) Liberators vastly increased the reach of the UK's maritime reconnaissance force, closing the Mid Atlantic Gap where a lack of air cover had allowed U-boats to operate without risk of aerial attack.