Ma'arif al-Qur'an
Mufti Muhammad Shafi1. These verses refer to the battle of Uhud.
The previous verses referred to Allah Almighty as the best of helpers'; recounted here are some incidents of Allah's help.
The word, سلطان sultan, rendered here as 'authority' includes all revealed or rational bases of their position. The promise of casting awe and fear into the hearts of the disbelievers in this verse was made in the back-ground of the battle of Uhud when the disbelievers of Arabia marched back to Makkah without any obvious reason and inspite of defeat overtaking Muslims (Baydawi). However, after having covered a certain distance on their way to Makkah, they awoke to their folly. When they thought of marching back to Madinah, Allah Almighty filled their hearts with such awe and fear that they could not muster the courage to do so. The most they could do was to hire a Madinah-bound villager to go there and tell Muslims that they were coming back. But, this whole deal came into the knowledge of the Holy Prophet ﷺ in Madinah through revelation. He marched to Hamra' al-Asad to apprehend them but they had already run away from there.
This was the background in which the present verse was revealed.
The verses that follow recount, as pointed out earlier, Allah's help and support for Muslims in the battle of Uhud.