Intelligence and training shape the night engagement

Radio interception, including a system called Headache, and Bletchley Park intelligence warned the British about the German sortie. Headache could detect transmissions over long distances, though its results varied with conditions. The force included the Type 1936A destroyers Z24 and Z32, the captured Dutch destroyer ZH1, and the Elbing-class torpedo boat T24. Jones divided the Tenth Flotilla into two four-ship divisions. The 19th Division, under his direct command, had practised the new night method, while the 20th included recently joined ships that were not equally familiar with it. Line-abreast radar tactics required the right displays and crews trained to hold station; imposing them across the whole flotilla risked collision and confusion. Jones organized the engagement around those differences in readiness.