President Volodymyr Zelensky on Sunday abruptly fired the head of Ukraine’s powerful domestic security agency, the SBU, and the state prosecutor general, alleging dozens of cases of collaboration with Russia by officials in their agencies. The sackings of SBU chief Ivan Bakanov, a childhood friend of Zelensky, and Prosecutor General Iryna Venediktova, who has played a key role in the prosecution of Russian war crimes, were announced in executive orders on the president’s website. The firings are easily the biggest political sackings since Russia invaded on 24 February, forcing the entire Ukrai…