 From reconnaissance photographs and pilots’ reports, Major Mullock had estimated that Friedrichshafen was defended by 16-20 heavy and 18-20 light flak guns and 25 searchlights, all within a 6-8 mile radius of the target.Harris considered these defences ‘comparatively light’.As the flares were laid, signalling imminent attack, the guns and searchlights sprang to life and opened up on the Pathfinders.