Why did the Turks adopt the Latin alphabet after WWI?

While there seems now to be a reaction, for decades following Ataturk it was part of the national identity to which the Turkish elite aspired to insist that Turkey was 'part of Europe' (which on usual geographical definitions only a small part of it, around Istanbul, really is). Likewise that it was a 'secular' state even if most Turks were Muslim.

This is probably part of the same tendency found to varying extents in many Asian countries in the late nineteenth and early twentieth centuries. Europe seemed so much more powerful, successful and more advanced that they wanted to copy it, in the hope they could become powerful, successful and advanced too.

This was partly a 'love-hate' relationship as one of the motivations was to beat the West at its own game. As in the late nineteenth & early twentieth century Japanese learned European methods to build up their armed forces and industry, and then used them to defeat a partly European power Russia in the Russo-Japanese War in 1904-5, and as Ataturk had done to fight off the Greeks, British and French to preserve Turkey as a new state.

The Turkish alphabet is based on Latin but with several changes to fit their language e.g. no letter 'w', an extra letter like an 'i' without a dot to make the sound 'uh', various vowels with umlauts over them which at least look Germanic.

Another part of Ataturk's modernisation & westernisation programme was to adopt German Criminal Law and Swiss Civil Law as the laws of Turkey.

Could part of what is happening in Turkey now be explicable by the fact that the relative economic, industrial and military decline of Europe and the West in recent decades, and gradual rise to power of other parts of the world, mean that it no longer seems self-evident that copying Europe and the West is the road to success?

Switching to Latin alphabet does not really mean making all nation suddenly illiterate as statistics show (see the reference in the end).

But of course this was a very radical measure, I agree, and a part of Westernization/modernization project. One of Kemal's goal was to decrease the role of religion and religious education; to separate literacy from religious education. I suppose this was a very effective measure from this point of view.

There were few similar cases in history.

When communists came to power in Russia at approximately the same time, they had similar projects of switching from Cyrillic to Latin. They did not implement it for various reasons, but later they forced other nations of Soviet Union to switch to Cyrillic alphabet. I mean the nations of Middle Asia, who used Arabic before, and Moldavia which used Latin. So this case is not unique in history. None of these switching led to widespread illiteracy. Probably the opposite is true. At least in the Middle Asia, the literacy rate sharply increased during the Soviet rule. It increased in Turkey as well.

Why did they use German assistance? Because of the close cultural and other connection with Germany which existed before the war. (This was actually one of the reasons why they entered the war on the German side). German defeat seems irrelevant for this particular project, and the project itself could be prepared before or during the war.

EDIT. As an evidence of what I wrote, here is the statistics of literacy rates in Turkey:

http://unesdoc.unesco.org/images/0000/000028/002898EB.pdf

(For Soviet Middle Asia I did not find the data but the increase in literacy rates was dramatic). And to answer some comments: I never wrote that Latin alphabet is simpler than Cyrillic. My point was only that this kind of reform can be relatively painless in what concerns literacy rates.

Turkey's post World War I leader, Mustapha Kemal, or "Ataturk" switched to the Latin alphabet as part of a mandate to break from the immediate, humiliating, and "Sultanic" past. A similar initiative was the move of the capital from Istanbul to Ankara.

Something like 8%-10% of the Turkish population was literate in 1927 (I couldn't find any earlier figures). So perhaps 90% of the population was illiterate.

Of the literate portion of the population, most knew, or had studied a European language, and would have been familiar with the Latin alphabet. Put another way, there were very few people who were both literate and unfamiliar with the Latin alphabet.

Changing to the Latin alphabet ( a modfied version thereof, actually), would not have rendered "100% of the population" newly illiterate. At most it would have been 8%-10%, and probably far less.

The people of the fallen Ottoman Empire and of Turkey up until then had used Arabic script, the same script in which the Islamic Quran is written in. One of the main reasons that Mustafa Kemal Ataturk transformed the script of the country of Turkey into Latin and in essence secularized the nation was to weaken the power of the Quran. Ataturk's policies almost seemed like borderline persecution against Muslims in a country dominated by this religion, as he abolishes garments sacred to the religion, such as the fez and the burqa, and allows clerical garb only in the mosque. He required the people of Turkey to wear Western clothing. Also, in 1925, the Turkish Historical Society rewrote the history of the country to downplay the Ottoman Empire and Islam, showing that Ataturk wanted to move as far away from the uber-religious state the country arose from. Of course, changing the script and language meant that more people would be illiterate, which is why Ataturk made elementary education free, universal, and obligatory.

To answer the question regarding certain parts of the new writing system being adopted from Germany, this may be because Turkey had the best relations with Germany at the time, so it would be easier to adopt their systems than those of a country they had considerably worse relations with, such as the UK or France. You may recall that Turkey also adopted secular law similar to that of the Swiss.

To summarize, Ataturk basically changed the script from Arabic to Latin to take away power from the Quran, and thus move towards being a secular state rather than one that is religiously driven.