This conjecture comes from Peter C. Perdue, the leading Western historian on the Qing conquest of the Mongols. In the conclusion of his masterpiece
China Marches West: The Qing Conquest of Central Eurasia, he notes that historian R. Bin Wong believes that had the Zheng regime had survived in Taiwan, Qing China could have been able to resist the West in the 19th century. Then he makes his own case on Zunghar survival:
But one could argue for the same outcome [of a 19th-century China able to militarily defeat the West] if a Mongolian state had held out in the northwest. (This scenario is more plausible than Wong's, in fact, since such a state [the Zunghars] did last for nearly a century, while the Zheng regime held Taiwan only from 1661 to 1683.) Then the Qing rulers would also have been interested in getting modern arms for their military expeditions, just as they had contracted for arms production from Jesuits in the seventeenth century. They could have used British military experience, and might even have invited the British to observe their campaigns, like the Jesuits who observed the eighteenth-century wars. Chinese armies had, in fact, come in contact with British arms during their incursions into Burma in the late eighteenth century but failed to borrow any new military technology from the experience. Had there been a strong Mongolian state, it is possible to imagine greater Sino-British military cooperation. The Chinese, also aware of the British presence in India, likewise might have realized potential British influence in Tibet, concerned as they were with keeping Tibet out of Mongol hands. This hypothetical argument highlights the openness of China's relations with foreign powers created by its frontier expansion, and points to the possibility of more fluid geopolitical alliances, each of which had effects on military balances, technological reform, and the political economy of trade.
Many others have made the same argument that the destruction of the Zunghars was at least partially responsible for Qing China's military deterioration. Tonio Andrade, in
The Gunpowder Age: China, Military Innovation, and the Rise of the West in World History, argues that the divergence between Qing and British forces during the Opium Wars was caused not only by European technology, but by the fact that the Qing did not fight a major external war between the destruction of the Zunghars and the coming of the British. Matthew Mosca, in
From Frontier Policy to Foreign Policy: The Question of India and the Transformation of Geopolitics in Qing China, points out that Qing China stopped formulating a unified foreign policy across multiple frontiers once the Zunghars were exterminated.
What does the forum think?