Bonus ( patrician ) Bonus ( , died 627 ) was a Byzantine statesman and general , one of the closest associates of Emperor Heraclius ( r . 610 – 641 ) , who played a leading role in the successful defense of the imperial capital , Constantinople , during the Avar – Persian siege of 626 . Biography . Almost nothing is known of Bonus ' s origins or private life . In a panegyric poem dedicated to Bonus in 626 , George Pisides calls him a " companion in arms " of Heraclius , possibly implying that Bonus accompanied him when he sailed from Africa in 610 to overthrow Emperor Phocas ( r . 602 – 610 ) . He is also known to have had an illegitimate son , John , who was sent as a hostage to the Avars in 622 . At this time , the Byzantine Empire was engaged in a prolonged struggle with its large eastern antagonist , the Sassanid Persian Empire . Over the past twenty years , Persian armies had managed to score victory after victory and capture most of the Byzantine Levant . In 622 , after securing peace with the Avars in the Balkans , Heraclius set out to campaign in person against the Persians . Bonus was left behind in Constantinople as the Emperor ' s deputy and guardian of his young sons , together with Patriarch Sergius . During Heraclius ' s absence on campaign for the next years , Bonus acted as the effective regent of the Byzantine Empire . The exact offices Bonus held are unclear : he held the rank of " patrikios " , and in the sources he is usually simply referred to as " the " magistros " " . Although this would usually imply the position of " magister officiorum " , Theodore Synkellos calls him " the general " ( " strategos " ) , possibly implying that he held the post of " magister militum praesentalis " . Modern scholarly opinion is divided between the two cases ; thus the " Prosopography of the Later Roman Empire " and Walter Kaegi support the latter thesis , while John Haldon notably supports the former . By 626 , Heraclius had scored several victories in the East and reversed the strategic situation in his favour , but the Persian general Shahrbaraz was still encamped with his army in western Asia Minor , close to Constantinople . At this juncture , the Persians came to an understanding with the Avars , raising the prospect of a combined siege of Constantinople . To that end , the Persians advanced , took and razed Chalcedon , opposite the Byzantine capital , and awaited the arrival of the Avars . Emperor Heraclius , having learned of the threat to his capital , decided not to return in person ; instead , he sent advice and reinforcements to Bonus , who proceeded to strengthen the city walls and gather provisions . The Avar army arrived before the city of Constantinople in July 626 . Proposals for a surrender by the Avar " khagan " were rejected by Bonus , and the siege began on July 29 . Bonus was the overall commander of the defenders . During the first five days of the siege , he sent repeated embassies to try to persuade the " khagan " to withdraw , offering money in return . On the fifth day , the Byzantine envoys encountered a Persian embassy in the " khagan " ’ s tent , a fact that underscored the danger the city would be in if the Avars ' Slavic allies managed to ferry the Persian army over the Bosporus strait . Thus , on the tenth day of the siege , August 7 , as the Avar assault peaked , Bonus lured the Slavs into a trap : the Byzantines had learned that the signal for the Slavic fleet to cross the strait and rendezvous with the Persian forces in Chalcedon would be the lighting of a great bonfire . Therefore , the Byzantines themselves lit a beacon in Blachernae , and as the Slavs made the crossing , the Byzantine fleet , standing by inside the Golden Horn , sallied forth and decisively defeated them . Following this success and the repulsion of the Avars from the walls , Bonus had to restrain the over - eager people of the city , including women and children , who wanted to rush out and capture the enemy siege engines . Instead , on August 8 , the Avars began withdrawing ; Bonus , Patriarch Sergius , and many people came to the Golden Gate to watch their retreat and the burning of the siege towers , set on fire by the Avars themselves . The Emperor ' s brother , Theodore , arrived soon after at the head of an army , and took up the running of affairs in the capital . Shortly after this , in early May 627 , Bonus died and was buried ( on May 11 ) in the Monastery of St John of Stoudios . Cistern of Bonus . Bonus also built a large cistern in the city ( Greek : ) , covered with a domed roof , close to the site of his own house . It lay to the northeast of the Church of the Holy Apostles , in the coolest part of the city . For that reason , Emperor Romanos I Lekapenos ( r . 920 – 944 ) built a palace there , the " New Palace of Bonus " . Theophano , the first wife of Emperor Leo VI the Wise ( r . 886 – 912 ) , also built a church nearby , St . Constantine of the Cistern of Bonus , where her body was eventually transferred , probably after the sack of the city in 1204 . This palace complex played a central role in the annual ritual commemoration of Constantine the Great , the city ' s founder , on May 21 , with the imperial family moving from the palace to Constantine ' s mausoleum in the Holy Apostles and back again .