The tribulation was shortened according to Christ so the idea of a 7 year trib (from Daniel) would be less than that and Rev 13 says the beast rules for 42 months. I call that the tribulation, being no more than 42 months total.
It starts with the rise of the ten horned beast which I view as a global empire or government...like the one world order. Something happens for it to come to power, possibly related to the wound that happened then healed. I believe the second beast of Rev is active at the same time as the first beast, just introduced to John in vision form after the vision of the first beast. So, the world controlled by one empire or government and one person leading it, with the ten horns/kings as sub-rulers of ten areas, possibly the entire world split up into ten areas.