The lofty and strong fort, which had been built by the side of a spring on the road leading from Hijr to Damascus in the border area of the territory of Syria, was called Tabuk. In those times Syria was one of the colonies of the Eastern Roman Empire. Its capital was Constantinople. Its frontier people were the followers of Christianity and the chiefs of the districts were satellites of the Ruler of Syria who himself took orders directly from the Roman Emperor.
The rapid penetration and expansion of Islam in the Arabian Peninsula and the brilliant conquests by the Muslims in the Hijaz were being noticed in areas beyond the Hijaz, and were making their enemies tremble and think of ways and means to check this tide.
The fall of the Government of Makkah, the adoption of Islam by the prominent chiefs of the Hijaz, and the bravery and sacrifices of the Muslim warriors, made the Roman Emperor decide to launch a surprise attack on the Muslims with the help of a well-equipped army, because he felt his empire to be in grave danger on account of the extraordinary influence and expansion of Islam. He was very much afraid of the increase in the military and political power of the Muslims.
In those days Rome was the only powerful adversary of Iran and possessed the greatest political and military strength. It was very proud on account of the victories which it had achieved against Iran and the defeat which it had inflicted on the Iranian army.
The Roman army, which consisted of 4000 mounted soldiers and infantry-men and was equipped with the armour of the latest model available in those times, encamped in the frontier strip of Syria. The tribes residing in the border areas (like the tribes of Lakham, 'Amilah, Ghassan and Jazam) also joined them and the vanguard of the army advanced up to Balqa '.[624]
News about the encampment of a group of the Roman soldiers in the frontier strip of Syria reached the Prophet through the caravans, which were