<P> Russian historian Lev Gumilev wrote that Xiongnu, Mongols (Mongol Empire, Zunghar Khanate) and Turkic peoples (Turkic Khaganate, Uyghur Khaganate) played a role to stop Chinese aggression to the north . The Turkic Khaganate had special policy against Chinese assimilation policy . Another interesting theoretical analysis on the historical - geopolitics of the Central Asia was made through the reinterpretation of Orkhun Inscripts . </P> <P> The region, along with Russia, is also part of "the great pivot" as per the Heartland Theory of Halford Mackinder, which says that the power which controls Central Asia--richly endowed with natural resources--shall ultimately be the "empire of the world". </P> <P> In the context of the United States' War on Terror, Central Asia has once again become the center of geostrategic calculations . Pakistan's status has been upgraded by the U.S. government to Major non-NATO ally because of its central role in serving as a staging point for the invasion of Afghanistan, providing intelligence on Al - Qaeda operations in the region, and leading the hunt on Osama bin Laden . </P> <P> Afghanistan, which had served as a haven and source of support for Al - Qaeda under the protection of Mullah Omar and the Taliban, was the target of a U.S. invasion in 2001 and ongoing reconstruction and drug - eradication efforts . U.S. military bases have also been established in Uzbekistan and Kyrgyzstan, causing both Russia and the People's Republic of China to voice their concern over a permanent U.S. military presence in the region . </P>

What types of physical features make asia a crossroad for trade