Flashpoints | Diplomacy | South Asia | Southeast Asia

Why Is China Watching India-Vietnam Relations Carefully

China appears to be closely monitoring the development of India-Vietnam relations, particularly in the areas of defense, maritime affairs, and strategic technology.

Indian Prime Minister Narendra Modi shakes hands with Communist Party of Vietnam General Secretary To Lam in New Delhi, India, May 7, 2026.

Since establishing relations in 1972, the India-Vietnam relationship has generally been seen as one of the most stable in the Asian geopolitical landscape. The two countries have maintained a foundation of traditional friendship, moderate economic cooperation, and gradually expanded defense engagements without creating significant strategic concerns for other major powers. Compared to hot topics such as the China-U.S. rivalry, the Taiwan issue, or the South China Sea dispute, the India-Vietnam relationship has rarely been the focus of attention for international policymakers.

However, that is changing rapidly. 

China appears to be closely monitoring the development of India-Vietnam relations, particularly in the areas of defense, maritime affairs, and strategic technology. While China likely does not view this development as a direct threat to its national security, its real concern lies in the increasingly clear convergence of strategic interests between the two countries in areas where China holds important interests, such as the South China Sea, the Indian Ocean, and a post-U.S. security architecture in Asia.

For a long time, China was relatively comfortable with India-Vietnam relations because cooperation between the two countries was largely symbolic. In fact, since the two countries established a Comprehensive Strategic Partnership (CSP) in 2016, defense activities have mainly been limited to delegation exchanges, small-scale exercises, and political dialogue. But in recent years, China watched this relationship become more substantive at a significantly faster pace.

Currently, India-Vietnam defense relations are no longer solely centered around friendly diplomatic statements. The two sides are expanding cooperation in areas of deeper strategic significance, such as submarine training, fighter pilot training, defense industry cooperation, sharing maritime situational awareness, and defense credit support. In particular, Vietnam’s access to the BrahMos supersonic cruise missile is becoming a symbol of the increasing strategic trust between Hanoi and New Delhi. 

During General Secretary To Lam’s visit to India from May 5-7, the two countries upgraded their relationship to a new level – “Enhanced Comprehensive Strategic Partnership” – and signed a joint declaration focusing on mutual assistance in defense industry development and maritime support.

From China’s perspective, these individual factors may not be enough to alter the regional military balance. But when viewed holistically, they reflect a much larger trend: India is gradually shifting from its position as a power center in South Asia to one of increasingly prominent security actors in Southeast Asia and the South China Sea.

China’s Geostrategic Concerns 

From ancient times to the present day, China has viewed Southeast Asia as a space where it has exclusive influence due to its geographical location, economic scale, and the region’s trade dependence on the Chinese market. However, with the increasing presence of the United States, Japan, and Australia, and now India’s growing involvement in Southeast Asian security issues, China’s strategic environment is becoming significantly more complex.

In this context, Vietnam has emerged as India’s most important partner in mainland Southeast Asia. Vietnam possesses a strategically advantageous position on the western coast of the South China Sea, has relatively strong military capabilities within ASEAN, and pursues a foreign policy flexible enough to cooperate with multiple major powers simultaneously. 

The South China Sea is at the heart of this concern. For China, the South China Sea is not just the site of overlapping territorial disputes but a space linked to its “core interests,” a matter of survival. It is a crucial strategic shipping lane for China’s trade and energy, and a key area for China’s ambition to become a global maritime power. China’s ability to project naval power into the Western Pacific and maintain its sea-based nuclear........

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