the kings of Characene vassals under Parthian suzerainty. After Mithridates extended Parthian control further west, occupying Dura-Europos in 113 BC, he became embroiled in a conflict with the Kingdom of Armenia. His forces defeated and deposed Artavasdes I of Armenia in 97 BC, taking his son Tigranes hostage, who would later become Tigranes II "the Great" of Armenia (r. c. 95–55 BC). The Indo-Parthian Kingdom, located in modern-day Afghanistan and Pakistan made an alliance with the Parthian Empire in the 1st century BC. Bivar claims that these two states considered each other political equals. After the Greek philosopher Apollonius of Tyana visited the court of Vardanes I (r. c. 40–47 AD) in 42 AD, Vardanes provided him with the protection of a caravan as he traveled to Indo-Parthia. When Apollonius reached Indo-Parthia's capital Taxila, his caravan leader read Vardanes' official letter, perhaps written in Parthian, to an Indian official who treated Apollonius with great hospitality. Following the diplomatic venture of Zhang Qian into Central Asia during the reign of Emperor Wu of Han (r. 141–87 BC), the Han Empire of China sent a delegation to Mithridates II's court in 121 BC. The Han embassy opened official trade relations with Parthia via the Silk Road yet did not achieve a desired military alliance against the confederation of the Xiongnu. The Parthian Empire was enriched by taxing the Eurasian caravan trade in silk, the most highly priced luxury good imported by the Romans. Pearls were also a highly valued import from China, while the Chinese purchased Parthian spices, perfumes, and fruits. Exotic animals were also given as gifts from the Arsacid to Han courts; in 87 AD Pacorus II of Parthia sent lions and Persian gazelles to Emperor Zhang of Han (r. 75–88 AD). Besides silk, Parthian goods purchased by Roman merchants included iron from India, spices, and fine leather. Caravans traveling through the Parthian Empire brought West Asian and sometimes Roman luxury glasswares to China. The merchants of Sogdia, speaking an Eastern Iranian language, served as the primary middlemen of this vital silk trade between Parthia and Han China. Rome and Armenia The Yuezhi Kushan Empire in northern India largely guaranteed the security of Parthia's eastern border. Thus, from the mid-1st century BC onwards, the Arsacid court focused on securing the western border, primarily against Rome. A year following Mithridates II's subjugation of Armenia, Lucius Cornelius Sulla, the Roman proconsul of