Bukhari

Hadith Commentary:
In that era, stable governments were established in Rome and Persia.
The Persian king was titled "Kisra" and the Roman king was titled "Qaisar."
In these countries, kings were regarded as gods, and the subjects used to worship them.
Ultimately, Islam came to put an end to such oppression and human suffering.
It raised the slogan of "La ilaha illallah" (There is no deity except Allah), declaring that the true sovereign is only Allah, Lord of all the worlds; those who pride themselves on kingship in this world and suck the blood of their subjects are false and deceitful.
Eventually, such oppression was eradicated forever from both countries, and during the era of the Caliphate, the Islamic flag began to wave over both lands.
Under its shade, people breathed a sigh of relief and tranquility, and this tyrannical monarchy was utterly annihilated from both countries.

Hadith Commentary:
➊ The Quraysh were mostly engaged in trade and would travel to Syria and Iraq for commercial purposes. When they became Muslim, they expressed concern that now the governments of Caesar and Chosroes would become obstacles to their trade. The Prophet (sallallahu alayhi wa sallam) reassured them by saying: "Now their backs have been broken." In the time of the Messenger of Allah (sallallahu alayhi wa sallam), Chosroes had perished and Caesar was still alive. Although there were Caesars and Chosroes after that as well, the awe and grandeur they once possessed had vanished, and they remained only Caesars and Chosroes in name.

➋ It should be noted that the king of Rome was called Caesar, and the king of Iran and Iraq was called Chosroes.

➌ According to the prophecy of the Messenger of Allah (sallallahu alayhi wa sallam), the Muslims conquered their lands and distributed their treasures in the way of Allah.

➍ The Messenger of Allah (sallallahu alayhi wa sallam) referred to war as deception and trickery, meaning that in battle, the enemy may be deceived through military strategies. However, this does not mean betrayal or breaking of covenants, because such actions are forbidden and unlawful.