Mackay became convinced that Herring was becoming increasingly difficult to work with as a result of stress and fatigue and asked Blamey for permission to relieve him. Blamey's response was characteristic: Morshead would be on the next plane. Yet Blamey maintained his faith in Herring, who retained command of I Corps on the Atherton Tableland, where he trained his men for the next operation. He did not know when or where this would be, so he focused on amphibious warfare. He created the 1st Beach Group and developed tactics and doctrine for amphibious operations based on his own experience in the New Guinea Campaign and reports from the Allied invasion of Sicily. The benefits of his work would be realised in the Borneo Campaign.