What strategy did God design and implement to start the 1st war between the believers under the leadership of the last prophet and the disbelievers in order to reveal the truth?

 

Verses 43-44 of Chapter 8:

And remember) when you (the Muslim army) were on the near side of the valley, and they on the farther side, and the caravan on the ground lower than you. Even if you had made a mutual appointment to meet, you would certainly have failed in the appointment, but (you met) that Allah might accomplish a matter already ordained (in His knowledge), so that those who were to be destroyed (for rejecting the faith) might be destroyed after a clear evidence, and those who were to live (believers) might live after a clear evidence. And surely, Allah is All-Hearer, All-Knower. And remember) when Allah showed them to you as few in your dream; if He had shown them to you as many, you would surely have been discouraged, and you would surely have disputed in making a decision. But Allah saved (you). Certainly, He is the All-Knower of that is in the breasts. And (remember) when you met, He showed them to you as few in your eyes and He made you appear as few in their eyes, so that Allah might accomplish a matter already ordained, and to Allah return all matters (for decision).