 Complete the following phrase:  The next substantial section of the Letter to survive tells of a recent to the author event - an invasion of Khazaria by HLGW most probably Oleg, prince knyaz of Rus, instigated by the Byzantine Emperor Romanus I Lecapenus. Romanus, a persecutor of the Jews, may have been seeking to counter Khazar retaliation for his policies. According to the Letter, HLGW was defeated by the Khazar general Pesakh in the Taman region. Faced with execution by the Khazars, HLGW agreed to attack Constantinople indeed, such an attack 