One did have the actual rise of Israel and that could not have happened unless Egypt was very much weakened. So, there was a large disruption.

My totally data-free hunch for part of what happened includes a large extensive drought (hints of that in the Bible even) and in addition, the Stepps. Inner Mongolia was continually spawning new tribes which pushed older ones further and rippled into Europe (long before it culminated in the Mongols). I think a drought might have caused a push into Europe which caused a ripple of refugees to cascade down southward hitting a region already in bad shape.

I'm further intrigued by an ISIS analogy. ISIS wasn't all that effective until the unemployed Sunni former members of the Iraqi army decided to join because they were experiencing ethnocide anyhow. Once these military men became fused with the religious fanatic leaders, ISIS became a force that took the world's top militaries to put it down.

My totally data-free hunch for part of what happened includes a large extensive drought (hints of that in the Bible even) and in addition, the Stepps. Inner Mongolia was continually spawning new tribes which pushed older ones further and rippled into Europe (long before it culminated in the Mongols). I think a drought might have caused a push into Europe which caused a ripple of refugees to cascade down southward hitting a region already in bad shape.