It's probably been around as long as there have been defeats in war.

E.g. [link|http://www.historyofjihad.org/china.html|History of the Islamic Jihad]:

In the Battle of the Talas river, the Qarluq Betrayal led to the defeat of the Chinese at Arab hands

On July 10th 751 AD the Arab and Chinese armies took to the field in Aulie-Ata on the backs of the Talas river. The Chinese cavalry seemed to initially overwhelm the Arab cavalry, but the Arabs had worked out a deal with one of the many Turkish contingents of the Chinese army viz., the Qarluq Turks, by promising them wealth and freedom in return for embracing Islam and betraying their Chinese masters. The Qarluqs who held a grudge against the Chinese for having reduced them to vassalage, viewed this as an opportunity to throw off the Chinese yoke by using the Arabs and had planned to later throwing off the Arab yoke as well and regaining their freedom from both the Chinese and the Arabs. The Qarluqs later played the main role in converting other Turkish tribes notably the Seljuks to Islam.

At the Battle of the Talas river, the Qarluqs betrayed their own people the Chinese and went over to the Arabs

At the battle of the Talas river where the Arab and the Chinese armies clashed, the Qarluqs who were a part of the Chinese army, opened a breach in their own ranks and allowed the Arabs to ford the river and helped them to encircle a part of the Chinese infantry butchering it to man. The Qarluq archers then surrounded their paymaster the general of the Chinese army Kao and shot him down. Now the Arabs followed their heinous practice of sticking the d\\severe head of an enemy and parading it before the enemy army. The Chinese not being used to such grisly war tactics, fell into confusion and disarray, not knowing who had betrayed them, and their General Kao. They broke ranks and fell into confusion, shaking the Chinese center, which was rapidly assaulted by the Arab heavy cavalry and destroyed. Thus due to Muslim subterfuge and savagery the infallible Chinese war machine gave way under combined assault of the Arabs and the traitor Qarluqs, and they faced a heavy rout. From behind the treacherous Qarluqs fell upon the Chinese animals, baggage trains and supplies carrying away all they could and receded back into the steppe.

The Arabs rounded up tens of thousands of Chinese and their non-Qarluq Turk allies and took them to Samarqand from where Abu Muslim sent them to Baghdad and Damascus to be sold as slaves, each worth a dirham. One Chinese survivor mentions being kept as cattle in the Arab prison camps. Abu Muslim and Ziyad made huge financial gains out of this slave trade and used it to pay their armies. More importantly the Arabs forced the Turk and Chinese prisoners to teach them the art of making siege trains and catapult machines, which the Islamized Turks were to use successfully in their attacks on the Byzantine cities.

Since the ultimate victors write the history, one has to take claims of "traitors" and "betrayal" with a grain of salt, I think.

I don't find Baker's article very pursuasive, myself. :-)

Cheers,
Scott.