Japan's Prime Minister Takaichi Sanae pledged to expand political, economic, and defense cooperation with ASEAN states in May, delivering her first major foreign policy address at Vietnam National University in Hanoi. She committed Tokyo to helping each ASEAN nation "acquire autonomy and resilience" amid intensifying geopolitical competition, updating her predecessor Abe Shinzo's Free and Open Indo-Pacific vision.
The choice of Vietnam wasn't accidental. It reflects how dramatically the relationship has shifted since the Cold War era, when Japan sided with China and the United States to isolate Hanoi over its Soviet alliance. That isolation lasted through the 1980s, as Vietnam hosted Soviet armed forces and occupied Cambodia. Japan didn't resume aid until 1992, after the Soviet collapse and the signing of the Paris Peace Agreements on Cambodia.
Building Economic and Military Capacity
Since resuming aid 34 years ago, Japan's Official Development Assistance to Vietnam has totaled approximately $29.3 billion, the largest of any of Vietnam's foreign donors. Japan is now Vietnam's third largest investor and fourth largest trading partner. The economic support aims to strengthen Vietnam's resilience against potential Chinese retaliation over maritime claims and reduce dependence on Chinese investment under Beijing's Belt and Road Initiative.
Defense cooperation has grown alongside economic ties. Japan agreed to provide Vietnam with six used vessels in 2014, the 12th year since that decision. Six years later, it agreed to technologies for building military ships to boost Hanoi's maritime capability. In 2021, Japan signed an agreement with Vietnam to allow the transfer of defense equipment and technology. Vietnam now falls under Japan's new Official Security Assistance under the 2022 National Security Strategy, established in the 4th year since its adoption.
This year, Tokyo lifted a ban on the export of lethal weapons, which would allow it to sell fighter jets, missiles, and warships. A recent proposal to jointly develop fast landing crafts suggests Japan supports Vietnam's ability to hold and possibly retake offshore islands. Unlike with other Asian countries, Japan's World War II crimes don't cloud bilateral relations with Vietnam. Vietnam is now one of the most pro-Japan countries in Asia.
Shared Maritime Security Concerns
The rapid reconciliation reflects the compatibility of the two countries' grand strategies. After China submitted its "nine-dash line" map to the United Nations in 2009, the 17th year since that move, maritime cooperation became one of the key tenets of bilateral ties. Tokyo and Hanoi discussed maritime cooperation as a way to safeguard regional peace in joint statements issued in 2010 and 2011. Before Beijing's move, Japanese and Vietnamese leaders didn't emphasize maritime security in their joint statements, though there were low-level defense exchanges.
The 2014 joint statement mentioned maritime security as an area of cooperation for the Vietnam-Japan partnership, the same year Japan provided Vietnam six vessels and one year after Japan protested China's declaration of an Air Defense Identification Zone over the East China Sea. The 2015, 2018, 2023 and 2025 joint statements also underlined the importance of maritime security.
Vietnam's post-1991 turn to the sea includes building a maritime economy, modernizing its navy and air force, and seeking peaceful settlement of South China Sea disputes through international arbitration. Japan's FOIP, first laid out in 2007, emphasized securing sea lanes stretching from the Indian Ocean to the Pacific Ocean for economic exchanges. Japan's 2013 National Security Strategy opposed unilateral attempts to change the status quo in the East and South China seas in violation of international law.
Multilateral Diplomacy Without Strings
Vietnam welcomes close maritime cooperation because it strengthens its multilateral foreign policy without forcing it to choose sides. Japan's constitutional limits on fighting overseas wars mean Vietnam can avoid the stigma of siding with one country against another, which is a principle of Hanoi's Four Nos doctrine. Japan's economic and military assistance also doesn't carry human-rights conditions or threaten the political authority of the Communist Party of Vietnam to the degree Western assistance can.
Japan's transfer of naval technology, platforms and expertise to Vietnam is meant to secure South China Sea sea lanes and the flow of oil from the Middle East to Japan. Japan's frequent port calls in Vietnam help build consensus and expectations for future U.S. port calls. Major U.S. Navy visits to Vietnam's ports are often preceded by Japan Maritime Self-Defense Force visits. Closer ties also let Japan deepen relations with ASEAN.
Vietnam established a partnership with Japan in 2002, a strategic partnership in 2009, and elevated Japan to Comprehensive Strategic Partner in 2023. Vietnam supports Japan becoming a permanent member of the United Nations Security Council, a position China opposes.
Beyond Maritime Focus
Analysts say there's room to expand cooperation beyond the maritime sphere. At present, the Vietnam People's Navy and the JMSDF lead defense cooperation, while land forces have played little role. Recommendations include supporting Vietnam's continental objectives, such as boosting Hanoi's land infrastructure to tighten connectivity with Laos and Cambodia and reduce their dependence on Chinese investment, exchanging views on how to use land forces in a maritime conflict, and developing weapons suitable for both continental and maritime domains such as missiles, drones and radars.
Japan has also pledged deeper cooperation on energy, critical minerals, semiconductors, supply chains and artificial intelligence. Defense cooperation is expected to rise as Japan expands its OSA budget.
Why This Matters:
The Japan-Vietnam partnership reveals how smaller and mid-sized nations are building security networks to protect their sovereignty and economic interests amid great power competition. Japan's approach offers an alternative model of security assistance that prioritizes capacity-building and multilateral cooperation over traditional military alliances. For Vietnam, the relationship provides economic development support and defense technology without the political conditions that can accompany Western aid, allowing Hanoi to strengthen its position while maintaining its non-aligned principles. The partnership's focus on maritime security and economic resilience addresses the structural vulnerabilities that smaller nations face when confronting more powerful neighbors. As regional tensions over territorial disputes continue, this model of cooperation may offer a template for other nations seeking to balance sovereignty concerns with the need for external support.