The Most Dangerous Border in the World The night before Beijing released its biennial defense white paper in mid-April, avowing that it would not "engage in military expansion," roughly 30 Chinese troops marched 12 miles into Indian-controlled territory. For at least the last five years, the Chinese military has routinely made forays across the disputed 2,400-mile-long Line of Actual Control that divides the two countries. The Indian government counted 400 similar incursions last year, and already 100 in 2013. But for the first time since 1986, the People's Liberation Army (PLA) troops refused to return home after being detected. They instead pitched three tents. New Delhi quickly summoned the Chinese ambassador, and Indian military officials protested to their Chinese counterparts. The Chinese soldiers responded by pitching two more tents, and erecting a sign, in English, that said "You are in Chinese side." Three rounds of unsuccessful negotiations broke off May 1, with Beijing demanding that New Delhi unilaterally withdrawal from its own territory before it would consider removing its encampment. Meanwhile, China's Foreign Ministry spokeswoman denied that PLA troops had even penetrated the boundary, paradoxically noting, "China is firmly opposed to any acts that involve crossing the Line of Actual Control and sabotaging the status quo." On April 25, India's External Affairs Minister Salman Khurshid situated the crisis in the context of Sino-Indian relations: "One little spot is acne, which cannot force you to say that this is not a beautiful face. That acne can be addressed by simply applying ointment. Khurshid will likely regret this remark, not only because it is a bad metaphor, but because it is wrong. Initial diplomatic efforts have failed, and even though war is unlikely, the standoff is a reminder of the deep and potentially dangerous rivalry that simmers below the Sino-Indian relationship. It is a strange time for China to pick this fight. With potential instability on the Korean Peninsula and sovereignty disputes in the East and South China Seas, it belies strategic logic for Beijing to open a new front of territorial revisionism. And it seems India agrees: One Indian general called the move "an inexplicable provocation." Perhaps it was a case of a PLA officer going rogue. Perhaps China wanted to send a message of strength in advance of high-level visits in May, when foreign minister Khurshid goes to Beijing and Chinese Prime Minister Li Keqiang visits Delhi on his first official trip abroad since taking office in March. Or perhaps, as many in the Indian media are speculating, Beijing is signaling it will no longer tolerate India's stepped-up patrols and infrastructure development along the border. While China's motivations remain unclear, the potential implications are massive. The Sino-Indian dynamic is often seen as a sideshow to Beijing's more immediate rivalries with the United States and Japan. But more intense strategic competition between India and China would reverberate throughout the continent, exacerbating tensions in Central Asia, the Indian Ocean, and Southeast Asia. Disruptions to the Asian engine of economic growth caused by these tensions could debilitate the global economy. The history of today's crisis predates the founding of both the People's Republic of China and the modern Indian state, in 1949 and 1947 respectively. The now-disputed border was established between Britain and a then-independent Tibet in 1914; China and India confirmed it as the de facto border in a 1954 treaty. In 1962, tensions stemming from India granting asylum to the then 27-year-old Dalai Lama, Chinese official maps claiming Indian-administered territory, and Indian border patrols in disputed areas boiled over into a one-month conflict. Although the Sino-Indian War was a decisive victory for China, it resulted in a return to the status quo. Mutual antagonism persisted for decades amid periodic border skirmishes. Only in this century have the two sides begun to improve relations, with bilateral trade growing from less than $3 billion in 2000 to over $70 billion in 2011. And leaders are sticking to a $100 billion target for 2015, despite a roughly 12 percent contraction in 2012. But as China's rocky relationship with its second largest trading partner Japan shows, economic interdependence is no guarantee of friendly relations, and severe trade imbalances in China's favor have been an ongoing source of tension in India. Numerous other friction points persist between the two nuclear powers. China frequently complains that India's offering of refuge to both the Dalai Lama and the headquarters of the exiled Tibetan government constitutes tacit support for China's territorial disintegration. And India is dismayed by Chinese plans to build a series of dams on the Brahmaputra River, which originates in Tibet but flows into India. Tens of millions depend on the river, and water competition between the two countries will likely continue to grow. Chinese expansion into the Indian Ocean -- which India regards as its backyard -- also raises hackles in New Delhi. Indian media reported in April that a classified Defense Ministry document alleged Chinese submarines have been making routine forays into the Indian Ocean. In February, a Chinese company assumed administration of Pakistan's strategic Gwadar port, reviving fears that China is seeking a stronger foothold along India's periphery. Geostrategic competition also extends to Myanmar, where China and India have long competed for influence, and is complicated by China's friendship with India's archenemy, Pakistan. And popular mistrust aggravates these political disputes: A 2012 poll by the Pew Research Center found that only 23 percent of both Indians and Chinese hold a "favorable" view of each other. Now, with Chinese troops in Indian-controlled territory, it is New Delhi's move. There will be immediate diplomatic implications on the content and atmospherics of upcoming high-level visits. The Indian military will have to consider augmenting its presence and capacity at the border, as it has during previous crises. Some Indian commentators are also suggesting that Delhi re-open the question of China's legitimate rule over Tibet, which would certainly anger Beijing. Over the last decade, India has conducted a landmark naval exercise with Japan, trained Vietnamese fighter pilots, and held increasingly sophisticated maritime exercises with Singapore. Even if diplomacy prevails and both sides find a face-saving resolution to the current standoff, the incident will likely cause India to strengthen its political and military relations with countries throughout East and Southeast Asia. Delhi should lend "a shoulder to countries such as Japan, Vietnam and even Singapore who are fearful of China's hegemonism," argues Swapan Dasgupta, a leading Indian journalist. A rerun of the 1962 conflict is unlikely; neither country is mobilizing for war and the presence of a few dozen PLA troops does not harbor the potential for rapid escalation like the high-seas gamesmanship in the South and East China Seas. Nevertheless, if the two sides cannot reach a lasting political solution soon, competition could overwhelm the positive tenor that has defined Sino-Indian relations in recent years. There are few worse things that could happen to Asia than its two biggest giants backsliding into rivalry.