The obvious and best strategy...

... is to achieve time travel and then invade the past.

The past has an inferior military, huge oil reserves, and smaller population. It is ripe for conquering.

I admit to some of that roal, >>8-suke. But oanly some. For other roal-sources, I make use of the back of boxes of breakfast cereal. (I am a cereal killer, I must advise you.)