The rise of India and China has attracted considerable academic and policy interest. Notably, the 2017 border standoff at Doklam, in Bhutan, was the focus of global attention as China publicly threatened to use force against India. But, the land border aside, there is also a growing rivalry at sea, especially in the Indian Ocean Region (IOR). 1 The accelerated growth of India’s economy and concomitantly of its military capabilities have generated the widespread perception that it is a rising power that will play an expanding role in the international system. This in turn has triggered widespread debate about the possibilities and limitations of India’s rise, as well as its potential to alter the military balance of power in Asia and the Indo-Pacific. India believes it is a benign power and has appropriated to itself the role of a “net security provider” in the region. This role has been increasingly challenged by China’s enhanced presence—its economic, diplomatic, and military power—in the IOR. As of now, in comparison with maritime tensions in East Asia—Sino-Japanese differences on the Korean peninsula and the multi-sided South China Sea dispute—the competition in the IOR between India and China is not as tense. However, with the launching of China’s ambitious Belt and Road Initiative (BRI) and reports of its new “base” in Djibouti, combined with the persistence of the India-Pakistan rivalry (which has been exacerbated by China’s military assistance to Pakistan), the potential for military tension remains substantial. 2 Apart from China’s increased presence in the Indian Ocean, one has also to consider US interests and ambitions since it is a de facto “resident power” by virtue of its military bases in the region. Complicating matters further and adding to the narrative of nascent great-power rivalry, the United States is currently transforming its relations with India while responding to the geopolitical challenge posed by the rise of China. How is the India–China rivalry playing out in the Indian Ocean? More specifically, is there a security dilemma between the two and, if so, how is it shaping their military strategies? What technological trends and developments in the naval arena are shaping this rivalry? And what is the US perspective towards these developments in the region?