BRITISH AIR DEFENSE IN WORLD WAR I:  United Kingdom. 1915-1918.  When the first German strategic bombing  attacks were initiated against the United Kingdom  in 1915, there was no system in place to provide a coordinated air and civil defense.  By mid-1918, an effective integrated defense provided London early detection and warning, fighter interceptor aircraft, and air defense artillery in a system that provided the model for future defenses against air attack.  When one considers that virtually every component of the system had to be invented, including ground observers, communications, anti-aircraft cannons, aircraft weapons systems, and command and control systems, at the same time that the threat moved from hundreds of pounds of bombs in a raid to thousands and from Zeppelins to four engine bombers, this was a remarkable achievement.

In 1915 when the Zeppelin campaign started, London was defended by 12 anti-aircraft artillery pieces and 10 small fighter detachments.  Reports of enemy airships were forwarded by telephone to the number for Anti-aircraft London from police constables, military installations, railway stations, and even lightships in the English Channel (presaging the days of picket ships and Texas Towers off the North American coast).  Individuals reporting Aircraft Reports were asked a detailed series of questions to determine the location, direction of travel, and description of the aircraft.  In the days when telephones were not universal, locating a telephone and forwarding such a report was not a rapid process - that may explain why some reports were forwarded by mail.  Even when Anti-aircraft London (coordinated by the Admiralty - the headquarters of the Royal Navy) received a report in a timely manner, the warning information then had to flow through the civilian telephone system, making fighter interception or coordinated anti-aircraft fire unlikely.

In 1916 responsibility for command and control was passed to the War Office (the Royal Army), and a number of new measures were implemented that proved adequate to meet the Zeppelin threat. Fighter bases were established at Sutton's Farm, Essex, Hainault Farm, Essex, and Hounslow, Middlesex.  A searchlight belt was established 25 miles from the coast stretching from Sussex to Northumberland.  A sound locator system was deployed to attempt to increase detections of the Zeppelins at night. 

The third component of detection was the establishment of the Metropolitan Observation Service (the precursor of the Royal Observer Corps).  Approximately 200 visual observer posts, staffed by police, were activated, located at sufficient distance from target areas to result in sufficient advance warning for effective tactical action.  These posts were connected to seven warning controls commanded by anti-aircraft defense commanders, with direct connections into the telephone trunk system.  Controls issued air raid warnings to districts. 

In 1917 the advent of the Gotha bomber threat led to consolidation of anti-aircraft defense under the command of Major General E. B. Ashmore, an artillery officer who was also a pilot and had commanded a Royal Flying Corps unit in France.  On 31 July 1917 the London Air Defense Area was activated; the increased efficiency of the defense was a key factor in the German decision to change to night bombing.  By late summer 1918 the completed defenses included:

Major General Ashmore was concerned with the speed and accuracy of visual detection and reporting.  Given the improvements of 1916 with the Air Bandit reporting system, priority telephone calls could reach the London Air Defense Area headquarters at Horse Guards in as little as 3 minutes, but more often in 9 to 12 minutes, and the quality of information was poor.  Significantly, the absence of reports did not necessarily mean that no enemy aircraft were operating near an observer post.  To remedy this Ashmore directed organizational changes, standardization in procedures, and new equipment.

This system would be readily recognized by Royal Observer Corps, Ground Observer Corps, or Womens Air Raid Defense veterans of World War II, as it is the essential model for all manual aircraft tracking and reporting systems.  The improvements resulted in reducing the detection to display on central control's map to 30 seconds on average.

Raid detections resulted in a series of warnings as shown in table 1.  These warnings flowed from central control to sub-controls to units for military operations and from central control to the Home Office for warnings to the civilian population.

Table 86-1.  London Air Defense Area Warnings

Warning Meaning
Readiness warning to military and police that a raid had been detected
Green air raid threatened
Red air raid imminent
White enemy aircraft clear of the district
Yellow cancel readiness measures
Turn In military units and police released

Sources: Wood, Derek, Attack Warning Red: The Royal Observer Corps and the Defence of Britain 1925-1975, London, United Kingdom, MacDonald and Jane's, 1976.  Cross, Wilbur, Zeppelins of World War I, New York, New York, United States of America, Barnes & Noble, Inc., 1991.

Entry 0386 - posted 12 August 2003