At Lord Cherwell's recommendation, Butt did an analysis of the effectiveness of Bomber Command. Reviewing 600 photoreconnaissance images, Butt did a statistical analysis of the attacks completed in June and July 1941. The resultant Butt Report showed that Bomber Command was having great difficulty delivering its bombs over its targets, with only 5% of bombers setting out bombed within of the target. This report was a key impetus to the formation of Bomber Command's Pathfinder Force, which greatly improved the accuracy and destructive power of Bomber Command.