Mundhir, together with his family at the capital, is treated well by Tiberius, who allows the Ghassanid king a comfortable residence and a subsidy, but denies him an audience.

Irfan Shahîd believes that this generous treatment, as well as the fact that he was not brought to trial for his supposed treason, indicate that Tiberius too did not believe the charges, but ordered the arrest chiefly to placate the strong anti-Monophysite faction in the imperial capital.

Maurice writes an encyclopedic work on the science of war (the "Strategikon"), which exercise a major influence on the military system.

Mundhir learns upon returning to his lands that a combined Persian-Lakhmid force is preparing another attack against the Ghassanid realm.

Immediately he sets out to meet them, engages their army and comprehensively defeats it, before going on to capture the enemy camp.

It is to be his last victory.

Despite his successes, Mundhir is accused by Maurice of treason during the preceding campaign.

Maurice claims that Mundhir had revealed the imperial plan to the Persians, who then proceeded to destroy the bridge over the Euphrates.

The chronicler John of Ephesus explicitly calls this assertion a lie, as the Byzantine intentions must have been plain to the Persian commanders.

Both Maurice and Mundhir write letters to Emperor Tiberius, who tries to reconcile them.

Finally, Maurice himself visits Constantinople, where he is able to persuade Tiberius of Mundhir's guilt.

The charge of treason is almost universally dismissed by modern historians; Irfan Shahîd says that it probably had more to do with Maurice's dislike of the veteran and militarily successful Arab ruler.

This is further compounded by the Empire's habitual distrust of the "barbarian" and supposedly innately traitorous Arabs, as well as by Mundhir's staunchly Monophysite faith.

Tiberius orders Mundhir's arrest, and a trap is laid for the Ghassanid king: summoned to Constantinople to answer charges of treason, Mundhir chooses his friend, the curator Magnus, a prominent aristocratic figure and close ally to emperors Justin II and Tiberius II, as his advocate.

Magnus owns property in Evaria (present Huwwarin) and finances many of its construction projects.

Here he has built a church as well as a wall surrounding it, and now calls on Mundhir to join him and the patriarch of Antioch Gregory in the dedication ceremony.

Mundhir arrives with only a small escort and is arrested by imperial troops stationed in secret at the location.

He is transported to Constantinople, joined along the way by his wife and three of his children.

Mundhir's arrest provokes a revolt led by his four sons, especially the eldest, al-Nu'man, a man described by John of Ephesus as even more capable and warlike than his father.

Following Magnus's departure from Huwwarin, al-Nu'man's troops raid and thoroughly plunder the city, slaying a number of its residents.

Thrace and Greece have been inundated by the Slavs during the four-year reign of Tiberius II.

The emperor, mortally ill, possibly from purposefully poisoned food, recognizes Maurice as his successor, betroths him to Tiberius' daughter Constantina, and crowns him emperor on August 13, one day before his own death.

Magnus had died shortly before Tiberius's own death in August 582, and with Maurice's accession to the throne, Mundhir’s son Nu'man journeys to Constantinople to achieve a reconciliation with the empire.

Instead, he too is arrested, tried, and sentenced to death, quickly commuted to house arrest.

The Western Turks meanwhile begin inroads across the Danube that will take them, within fifty years, into Macedonia, Thrace, and Greece.

The Ghassanid army has for two years launched raids into the imperial provinces from their bases in the desert, even defeating and killing the imperial dux of Arabia in a battle at Bostra.

Tiberius reacts by raising a Chalcedonian brother of Mundhir to the Ghassanid kingship.

A large army with Magnus at its head is dispatched east to counter Nu'man and install his uncle as king.

The latter is swiftly done, but the new king dies after only twenty days.

Magnus also has some success in subduing or subverting the allegiance of some minor Arab tribes away from the Ghassanids.