was one of the reserves of the northern front of polish defences, created on september 1, 1939. according to plan west, it was supposed to defend the line of the narew river from wehrmacht units advancing from east prussia. due to rapid german advance, the group withdrew towards the bug river, and on september 11, polish commander in chief edward rydz-śmigły ordered general wincenty kowalski, commandant of operational group wyszków, to merge his unit with northern front under general stefan dąb-biernacki.