Which one and why ?WW I & WW II battles not included in this topic.

 Chalons is possibly one of the more important battles and decisive for Europes future, not decisive in terms of the outcome of the actual battle since neither Rome nor the Huns won the day, in terms of the consequences it was huge. 

 Had Attila won at Chalons then western europe would have been ravaged beyond recognition and perhaps entered a dark age that may have lasted much longer than it did, with unimaginable consequences.

If the Arabs had lost Qadasiya then there would be no Islam today ro at least it would be confined and would probably have been afflicted with the same fate as Juda'ism.  Infact, Muslims and Jews would have been perfect religious allies today.

Qadisiya is the death of Persian civilization no doubt. It is more important than many of the others above...

There was bitter enmity between Christians and jews long before there were any Muslims, who knows where that would have escalated to.

It was the end of non-Islamic Iranian civilization, and by no means the end of Iranian civilization which became integral to that of Islam and was also perpetuated by many Turkic dynasties.

The Jews massacred 90,000 Christians when the Persians captured Jerusalem in 614.

Ever read certain verses from the Talmud? They encourage hate and murder of Christians.

In Ottoman Era,Jews and Muslims were getting on well Zagros.

I would not expect Iranians to like Islam and its rise and occupation over Persian world, but there are more important results of Qadisiyah:

1) End of Persian civilization, start of Islamized Arabo-Persian civilization.

2) Starting of a more Dynamic rival to the Christian world.

3) Neighboring of Islam and Turko-Mongols of Central Asia... 

In all eras previous to modern times Jews and Muslims got on.

And nowhere in this thread did I show resentment for what happened as you insinuate for whatever reason, all I said is that as far as history is concerned (in my opinion) Qadasiya was the most decisive in shaping today's world.

yes but look at our world now.  Even the Muslim world (the modern parts) use legal systems related to English law.  the Britishs EMpire conained 1/4 of the worlds population. I dont think even now the Islamic faith can claim a quarter of the world.  Religion is totally irrelevant compared to th espread of technology, political systems, and legal practices. 

That doesnt mean there would be none, just that it would be delayed. Perhpas they would try harder from Europe to get their hands on Chinese science as well?

 Think people have to realise to that the Persian army left alot to be desired, its cavalry was very good aswell as its archers but its infantry was largely shockingly poor, men pulled from their farms given a spear a wicker shield and told to stand against a macedonian phalanx.

 An army of 250,000 men should be able to smash an army of 40,000, it surely points to a problem with a large portion of the Persian army, I dont doubt Alexander was a better general, but had the Persian army or atleast more of it had been even relatively decent quality then sheer weight of numbers would eventually have crushed the much smaller Macedonian army.

 Personally I dont see the big deal about routing an army that was filled with largely unwilling or poor quality troops who would much rather of been at home than fighting for the King of Kings, with an army that was full of battle hardened veterans who were infinitely superior in almost every way.

English common law is largely derived from Roman law, btw.

The weak ability of persian,the unfit weapon against Greek waepon,mixed army from defeated nation by persian,phalanx then Alexander the reasons of defeated at Arbila.

 Good for you, unfortunately for me I thought Hollywood might just make a decent and accurate historical movie for once and watched it, alas my disappointment was even more than when I watched "Kingdom of heaven"  which is an amazing achievement I suppose.

Greatest battle is the battle of Talas, where Muslim troops defeated the Chinese Army and their allies.

Result: Opened the door of Islam to Central Asia, Hence!! Turkic tribes became Muslim, hence!! they build their current glory history. From nomadic steppe grazing tribes to Seljuks & Ottoman empires.

Outstanding addition (not to mention a way too unkown battle in the West) cog gec.

No question that the Arab victory (I think they outnumbered the Chinese by more than 3 to 1) had huge ramifications on the future. The Arabs were put in a position to extend their Islamic influence throughout central Asia and take control of the important silk routes. The Chinese lost a good amount of power and their westward advance was halted. Muslim shipping in the Indian Ocean improved, which restricted the ocean's contacts with Hinduism and Buddhism. But the Muslims were never able to take control of the Himalayan northern borderlands, and much internal strife ensued among them. Paper manufacturing was first spread to Samarkand and Baghdad, then from there carried to Damascus, Cairo, and Morocco, and finally entered Europe through Italy and Spain. This was transmitted when Chinese prisoners who knew how to make paper, which was discovered in China at least 650 years earlier, were taken by the Arabs at the Talas River. Battle of Talas also led to the An-Lushan rebellion, which broke out in 755. This event paralyzed China for years and weakened the T'ang dynasty until it collapsed a century and a half later. 

Another big one was Manzikert, fought in 1071. Alp Arslan's defeat of the Byzantines left Asia Minor open for him, and Europe probably felt the Byzantines were not capable of checking the Muslims, leading to the crusades.

Thanks Spartan JKM   

Well, my measurement of decisive battles is their effect or aftermath. At the battle of Talas, nothing really was of a drastic change right away after the battle. But its effect later proved to be a huge change to the world for the coming thousand years.

As Spartan mentioned, without Paper discovery which happened at Talas, no Baghdad library would have been built or Cordoba library would have flourished with over 200,000 book. Paper has changed the world and elevated the Islamic civilization to be the leader for another 700 years at least.

Second, most turkic tribes became Muslim gradually as Muslim dominated the trade routes and that geographical area. From the depth of those steppe, came the ancestors of Seljuks and the Ottoman empires, who are one of the greatest empires in history.

P.S: 150,000 Muslim soldiers Against 30,000 Chinese soldiers. that is 5 times actually. http://www.absoluteastronomy.com/encyclopedia/b/ba/battle_of_talas.htm - http://www.absoluteastronomy.com/encyclopedia/b/ba/battle_of _talas.htm

^cok gec....

Please check your facts. After Talas, door of islam did not open to Central Asia. Probably you were educated in Turkey as far as I can see.

The problem comes with a misinterpretation of Barthold' s papers. Talas removed the Turkic and Chinese peril from Transoxianna (Maveraunnehir) which is Iranic Central Asia.

Even after 400 years later than Talas, Karluk Turks were still Nestorian Christians.

Conversion of Turks to Islam is just happened with the massive missionaries and Satuk Bugra Khans decisions. Turkic embracements started in 900s... These little clans/subclans immigrated to Persia, later they will establish the Ghaznawid Empire.

I have always wondered why people make such a great deal with Talas.  Talas had no bearing on the Chinese withdrawal from Central Asia.  The Tang Army had around 300,000 border troops, but only 30,000 were used at Talas.  The Korean general who commanded the army at Talas was never demoted, thus showing the relative little importance of the battle.  The Tang Empire retained its garrisons in Central Asia and East Turkestan after Talas. 

It was the Anlushan Rebellon in A.D.753, two years after Talas, by 150,000 border troops, and the subsequent civil war and warlord struggle that prevented the Tang Empire from logistically maintaining its garrisons in Central Asia and East Turkestan, and many of them fell to Tubo.

How did Talas lead to the Anlushan Rebellion? Anlushan planned his rebellion for years.  He was stationed in modern day Peking, while Talas took place in Central Asia.  Anlushan harbored rebellious intentions way before Talas.

Hmm, if we cannot agree on its military importance which can be easily disputed, can we agree that it is important for its aftermath effect? If Paper didn't come with Talas, imagine how many centuries we need to transfer this valuable discovery from Baghdad to Andalucia and to Europe?

Maybe Wikipedia has some mistakes here. I just noticed because Ummayed empire lasted from 661 AD to 750 AD. Very interesting. Thanx for bringing this up.

Nope! I didn't study in Turkiye or in Turkish. I'm not even a turk

In my opinion, the most decisive battle in whole history is the battle of Metaurus. This battle is decisive for Europe destiny and very interesting for risky tactics of a great forgotten man, the consul Claudius Nero.