Imagine you are a a god watching down on the world altering events to suite your interests making small changes that ripple through time altering the big picture.
The goal of the game is to guide the world toward peace in the time allowed. As the player progresses the conditions required to win will become stricter from require peace treaties to complete world disarmament.
The player guides the world by jumping to different points in time and altering specific events so that it goes on their desired course. However they must be careful that the changes they make do not have negative consequences. to alter the events players can use things like the wind to blow away documents or alter the path of objects, delay people or events so that they occur at the right time, or insure that the right people come up with the right ideas.
The player must avoid being to obvious in the methods they use (sending storms to stop all fights). So that the inhabitants of their world do ot suspect some for of divine intervention.
Image Source: http://img3.wikia.nocookie.net/__cb20141115140115/interstellarfilm/images/3/36/Nl8KjBO_-_Imgur.png