a specific muzzle velocity, zero wind, air temperature and density, and propellant temperature. In practice, this standard combination of conditions almost never existed, they varied throughout the day and day to day, and the greater the time of flight, the greater the inaccuracy. An added complication was the need for survey to accurately fix the coordinates of the gun position and provide accurate orientation for the guns. Of course, targets had to be accurately located, but by 1916, air photo interpretation techniques enabled this, and ground survey techniques could sometimes be used. In 1914, the methods of correcting firing data for the actual conditions were often convoluted, and the availability of data about actual conditions was rudimentary or non-existent, the assumption was that fire would always be ranged (adjusted). British heavy artillery worked energetically to progressively solve all these problems from late 1914 onwards, and by early 1918, had effective processes in place for both field and heavy artillery. These processes enabled 'map-shooting', later called 'predicted fire'; it meant that effective fire could be delivered against an accurately located target without ranging. Nevertheless, the mean point of impact was still some tens of yards from the target-centre aiming point. It was not precision fire, but it was good enough for concentrations and barrages. These processes remain in use into the 21st century with refinements to calculations enabled by computers and improved data capture about non-standard conditions. The British major-general Henry Hugh Tudor pioneered armour and artillery cooperation at the breakthrough Battle of Cambrai. The improvements in providing and using data for non-standard conditions (propellant temperature, muzzle velocity, wind, air temperature, and barometric pressure) were developed by the major combatants throughout the war and enabled effective predicted fire. The effectiveness of this was demonstrated by the British in 1917 (at Cambrai) and by Germany the following year (Operation Michael). Major General J.B.A. Bailey, British Army (retired) wrote: An estimated 75,000 French soldiers were casualties of friendly artillery fire in the four years of World War I. Precision-guidance Modern artillery is most obviously distinguished by its long range, firing an explosive shell or rocket and a mobile carriage for firing and transport. However, its most important characteristic is the use of indirect fire, whereby the firing equipment is aimed without seeing the target through its sights. Indirect fire emerged at the beginning of the 20th century and was greatly enhanced by the