Verified answer

According to him, the motor of History is Providence. It can be compared to Destiny, but he didn't use this definition since it had a religious connotation, which was not well seen at the time when it came to reasoning. He rather associated Providence with Nature, assuming Man has a nature.

As for Providence, it's kind of an evolution of Man towards an ideal, positive World. This evolution needs wars, as wars teach us what is bad, what is misery, thus giving Man the opportunity to change in a positive way. You could say wars are a necessary evil for a good cause. The other particularity of Providence is that it takes place on a very wide time span, so one individual, in his whole life, will never see the achievement of our species. However, we should act the best we can to help Providence, and thus providing our descendants the best World possible.

Hope it helps, but don't forget it's a very short summary.