From the description given in the Sixth Bowl of Wrath, we see that there are drastic climatic changes and the great river Euphrates evaporates and around the same time, there is a massive invasion from China [Kings of the East] via Tibet, Pakistan, Iran and Turkey.
It also becomes clear from this description of the start of the Third World War that it centers around the Middle Eastern nations. The Kings of the East [China] along with the nations allied with them gather around the region of the central battlefield, which is the area around Megiddo. It is also clear that not all the nations at war will gather in the single Plain of Esdraelon but the battle lines will stretch for thousands of miles through Iraq, Syria, Turkey, Egypt, Africa, Europe and the Meditation. The Plain of Esdraelon will only be the first line of conflict, which heralds in the most destructive Third World War.
However, the 6th Bowl of Wrath does give the reason for this invasion nor does it give the duration of the Third World War.
The 7th Bowl of Wrath is descriptive of the Ultimate Earthquake, which changes the Map of the World. This is also an indication that the Ultimate Earthquake follows the massive destruction of the Third World War and causes more unimaginable destruction.
Not a happy future to look forward to, however, there is a Silver Lining a New Age or the Age of the Kalki Avatar of Vishnu will dawn after the tribulation.