We all know about the arguments for islam, like the scientific miracles in the Qur'an, the predictions therein and the miracles and predictions by the Prophet salallahu 'alayhi wa sallam. Also, his sincerety and simple lifestyle all make up a strong argument for islam.
One of these that I didn't think about before is the following:
I watched "The Sirah" with Yasir Qadhi last week and he said that the Prophet salallahu 'alayhi wa sallam told the Meccan leaders that if they said one kalimah, then they would rule the world. They answered that they would say ten kalimahs if the result would be that they would rule the world, but when the Prophet told them to say la ilaha ill Allah, they refused.
So, the promise was that the arabs that accepted islam would eventually rule the world.
Within a record period of time, muslims conquered basically the whole known world. From India in east to Spain in west. Even non-muslims are astounded. Considering that the Prophet barely survived the Meccan persecution and that the muslims were nearly annihilated at the battle of the trench, this evolution of things is astounding. It's a miracle.
So, the fact that the Prophets promise that the one's that accepted islam would rule the world is another proof for islam.
Here's a relevant link:
Scroll down to "Islam, past, present & future" and press the "Video"-button to the left.