▁city ▁of ▁Constantin ople ▁in ▁July ▁ 6 2 6 . ▁Pro pos als ▁for ▁a ▁surrender ▁by ▁the ▁A var ▁k h agan ▁were ▁rejected ▁by ▁Bon us , ▁and ▁the ▁sie ge ▁began ▁on ▁July ▁ 2 9 . ▁Bon us ▁was ▁the ▁overall ▁commander ▁of ▁the ▁def enders . ▁During ▁the ▁first ▁five ▁days ▁of ▁the ▁sie ge , ▁he ▁sent ▁repeated ▁emb ass ies ▁to ▁try ▁to ▁persu ade ▁the ▁k h agan ▁to ▁withdraw , ▁offering ▁money ▁in ▁return . ▁On ▁the ▁fifth ▁day , ▁the ▁By z antine ▁en vo ys ▁encountered ▁a ▁Pers ian ▁emb ass y ▁in ▁the ▁k h agan ’ s ▁tent , ▁a ▁fact ▁that ▁unders cor ed ▁the ▁danger ▁the ▁city ▁would ▁be ▁in ▁if ▁the ▁Av ars ' ▁S lav ic ▁al lies ▁managed ▁to ▁fer ry ▁the ▁Pers ian ▁army ▁over ▁the ▁Bos por us ▁stra it . ▁Thus , ▁on ▁the ▁t enth ▁day ▁of ▁the ▁sie ge , ▁August ▁ 7 , ▁as ▁the ▁A var ▁assault ▁pe aked , ▁Bon us ▁l ured ▁the ▁S lav s ▁into ▁a ▁trap : ▁the ▁By z ant ines ▁had ▁learned ▁that ▁the ▁signal ▁for ▁the ▁S lav ic ▁fleet ▁to ▁cross ▁the ▁stra it ▁and ▁rende z vous ▁with ▁the ▁Pers ian ▁forces ▁in ▁Chal ced on ▁would ▁be ▁the ▁light ing ▁of ▁a ▁great ▁bon fire . ▁Therefore , ▁the ▁By z ant ines ▁themselves ▁lit ▁a ▁be acon ▁in ▁Bla ch ern ae , ▁and ▁as