How did the Muslims conquer so much so quickly?

(Inspired by this thread on the Mongols.)

I seem to recall that before Muhammad the Arabian peninsula was a complete backwater sparsely populated by nomadic tribesmen that had never been more than a nuisance to the Mediterranean powers. Yet within 150 years of Muhammad’s death they had conquered virtually all of the Persia Empire and half the Roman one. How did they pull it off? Granted the Romans and Persians had weakened each other through a long war, but still, where did the Muslims get the manpower to pose a significant threat to either of these big empires?

And Spain and into France.

I could elaborate, if you wanted, but the short answer is that the Persians were on the verge of collapse, and that the Romans, while somewhat more stable domestically, didn’t have a large enough army to defend its borders or replace its losses.

150 years is forever.

Dude. You asked the exact same question ~ 2 years ago in GD :p.

http://boards.straightdope.com/sdmb/showthread.php?t=425580

LOL … whoops. I have a bad habit of forgetting what I’ve asked.

Yes, well, this will be covered on the final exam.

The 160 million years the dinosaurs were dominant is even longer, but people tend to clump all of them into one timeframe. More recently, I’ve noticed a tendency to treat the period from the middle of the 19th Century to the First World War as fairly monolithic, under the umbrella terms Victorian and Edwardian.

(Side note: The oldest living people were born in the middle 1890s. The vast majority of the 19th Century is now lost to living memory. For reference, the last verified Civil War veteran, Albert Woolson of the Union Army, died in 1956. (The last verified Confederate veteran was named Pleasant Crump. He died in 1951.))

History telescopes in behind us. We don’t see it as through a glass, darkly, so much as through a funhouse mirror distorted: We often get confused about how long something has been going on, whether a habit is recent or established, and we get shocked by how long we’ve been somewhere.

So 150 years is forever. In 2011, it will have been that long since the start of the Civil War, so get ready for a bombardment of merchandising in about a year and a half. However, our perception of time is pretty much screwed up when dealing with events that long ago.

All sorts of reasons, I’d recommend the book Sea of Faithwhich goes into this in some detail. But one of the big reasons is internal religious divisions within the Byzantine empire.

Most of the grunts (and rural populations in the conquered regions) were Monophysite whereas the Byzantine elites who led them were Chalcedonian, who considered the Monophysites heretics. Its an extremely obscure religions disagreement (effectively about where to put a comma in the religious creed), but it led directly to the collapse of the Eastern Christian world. As it meant the foot soldiers had much less reason to fight than their muslim counter parts, and the conquered Monophysite Christians often welcomed the Muslims as relief from their Chalcedonian overlords.

And people laugh at us for insisting on the serial comma…

O/T, pardon the sidetrack, but one interesting exercise I like to do when thinking about the past is to double the number of years back and compare those two time periods.

For example, when thinking of how life was like in 1940, remember that people in 1940 were thinking the same things about life in 1871.

I’m in my mid-30s. I had a grade school teacher whose mother rode a horse to school and she lived to see man land on the Moon.

A lot can happen in a short period of time!

Or to put it another way: 150 years of effort, starting with a couple thousand enthusiasts, can get you pretty much anywhere, if you’re lucky and clever.

And have some brilliant generals., possibly the best field commanders of all time.