On 14 August 1944 SS Chief Heinrich Himmler received the mandate to have former Social Democratic (SPD) and Communist Party (KPD) officials detained. The mass arrest, which was estimated to cover more than 5,000 former politicians, should take no account of whether or not those detained were still engaged in opposition activity, and was not connected with the search underway for the July assassination plotters. On Thursday 17 August 1944 all leading Gestapo officers in the country received a secret telex from Department 4 of the Reich Security Main Office ("Reichssicherheitshauptamt"; RSHA). The telex contained notification from Gestapo Chief Heinrich Müller, regional Landtags or city councils who had been members of the (till 1933 legal) SPD and KPD (parties) along with all trades union and party officials of the SPD, without regard to whether or not they were currently facing investigation, were to be detained. Those aged more than 70, those who were ill and those who had been "of service to the system" [since 1933] should be spared from arrest, however. The arrests were to happen nationwide during the early hours of 22 August. Orders were that detainees should then be taken without delay to the nearest concentration camp and taken into what was designated "protective custody" by the RHSA. Additionally, by 25 August Gestapo officers of the RHSA should then report the total numbers arrested, analysed according to political party and according to political functions. Himmler's orders arrived under the heading Aktion Gitter. On 21 August the order was extended so that pre-1933 assembly members from the old Centre Party were also to be detained, although this broadening of the scope of The Aktion was partially rescinded two days later.