Operation Bagration ( ; , Operatsiya Bagration ) was the codename for the Soviet 1944 Belorussian Strategic Offensive Operation , ( , Belorusskaya nastupatelnaya Operatsiya `` Bagration '' ) a military campaign fought Hostile_encounter between 23 June and 19 August 1944 in Soviet Byelorussia in the Eastern Front of World War II .