A shootout between Ukraine’s two most powerful intelligence services left three military intelligence officers wounded on Wednesday. The gun battle in a Kyiv residential neighborhood brought a long-running feud into public view.

One Ukrainian intelligence source described it to me as an internal dispute between the Security Service of Ukraine (SBU) and the country’s military intelligence service (HUR). A second, high-level source said the shooting began after HUR personnel tried to recover one of their officers from SBU custody. The detained man was Stepan Kaplunov, deputy commander in the Russian Volunteer Corps, a formation of Russian citizens fighting for Ukraine under HUR.