Japan’s Prime Minister Takaichi Sanae said in an address to Vietnam National University in Hanoi in May that Japan remained committed to the Free and Open Indo-Pacific concept, while Tokyo pledged to increase political, economic, and defense cooperation with ASEAN so each state can "acquire autonomy and resilience" in the face of intensifying geopolitical competition. The speech, Takaichi’s first public one on updating Abe Shinzo’s FOIP vision, was delivered in Vietnam. That choice said plenty. The great powers talk about autonomy while tightening their own grip on the region’s trade routes, militaries, and supply chains.
Who Has the Power
The Japan-Vietnam relationship has changed dramatically since the end of the Cold War, but the machinery underneath it still looks familiar: states, fleets, aid packages, and defense deals arranged from the top down. During the Third Indochina War, from 1978 to 1991, Japan sided with China and the United States to isolate Vietnam because Vietnam was a Soviet ally. Japan’s position reflected fears of a Soviet invasion from the north in the late 1970s. Beginning in May 1978, Moscow increased the number of troops stationed on the Soviet-controlled Southern Kuril Islands to 6,000. The Soviet Pacific Fleet also grew until it became the largest of the four Soviet fleets, and the Soviets deployed SS-20 intermediate-range ballistic missiles to the Asia-Pacific theater.
Japan then signed a Treaty of Peace and Friendship with China in August, including an anti-hegemony clause implicitly directed against the Soviet Union. It strengthened naval cooperation with the United States and took part in the Rim of the Pacific Exercise for the first time in 1980. Japan also built up its own navy and air force to balance the Soviet threat and hedge against possible U.S. retrenchment from the Asia-Pacific. The aim was to protect the home islands and the sea lines of communication up to 1,000 nautical miles from Japan’s coasts. Ordinary people rarely get a vote in these calculations. The fleets do.
Who Gets Crushed
Japan had provided economic aid to Vietnam in 1975 and 1976 to help it recover from the Second Indochina War, but Tokyo froze that aid after Hanoi formally allied with Moscow in November 1978 and invaded Cambodia in December to topple the Khmer Rouge. Japan did not condemn China’s retaliatory invasion of Vietnam a few months later. In April 1979, Japan conditioned the resumption of aid on Hanoi not establishing permanent Soviet military bases in Danang and Cam Ranh Bay, which Tokyo feared would threaten oil supplies from the Middle East. As Vietnam hosted Soviet armed forces and occupied Cambodia during the 1980s, Japan added another condition: Vietnam’s troop withdrawal from Cambodia. Japan did not resume aid until 1992, after the Soviet collapse and the signing of the Paris Peace Agreements on Cambodia.
Since then, Japan’s Official Development Assistance to Vietnam has totaled approximately $29.3 billion, the largest of any of Vietnam’s foreign donors. Japan is Vietnam’s third largest investor and fourth largest trading partner. The numbers sound generous until you read the fine print of power. Aid, investment, and trade all move through state channels, and the people at the bottom live with the consequences of decisions made elsewhere.
What They Call Cooperation
The two countries began low-level defense exchanges around the same time, with agreements on Japanese ships’ port calls in Vietnam, joint search-and-rescue operations in the South China Sea, and training Vietnamese students at Japan’s National Defense Academy. In 2014, Japan agreed to provide Vietnam with six used vessels, and 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 falls under Japan’s new Official Security Assistance under the 2022 National Security Strategy. In 2026, Tokyo lifted a ban on the export of lethal weapons, which would allow it to sell fighter jets, missiles, and warships.
Unlike with other Asian countries, Japan’s World War II crimes do not cloud bilateral relations with Vietnam. Vietnam is now one of the most pro-Japan countries in Asia. Vietnam established a partnership with Japan in 2002, a strategic partnership in 2009, and elevated Japan to Comprehensive Strategic Partner in 2023. The article says the quick pace of reconciliation reflects the compatibility of the two countries’ grand strategies. During the Third Indochina War, Vietnam prioritized western and northern Indochina over the South China Sea, while Japan focused on defending against a Soviet invasion from the Southern Kurils. After the war, Hanoi and Tokyo shared concerns about China’s contestation of their maritime sovereignties. Vietnam began to look east to the sea, while Japan pivoted to the southern islands and treated maritime zones outside Northeast Asia as vital to its security. Japan supports combining the East China Sea and the South China Sea into a single theater of operation.
Political leaders in both countries developed grand strategic visions that align in economy, military affairs, and diplomacy. 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 2010 National Defense Program Guidelines called for a new "dynamic defense force" away from Cold War-era equipment and organizations capable of responding to threats from the southwest, and its 2013 National Security Strategy opposed unilateral attempts to change the status quo in the East and South China seas in violation of international law.
Joint statements show how the two countries’ grand strategies have evolved. Before China submitted its "nine-dash line" map to the United Nations in 2009, Japanese and Vietnamese leaders did not emphasize maritime security in their joint statements, though there were low-level defense exchanges. Statements released by both sides in 2007 and 2008 did not mention maritime cooperation, and economic cooperation was the main topic. After Beijing’s 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. 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.
Japan’s aid and military support to Vietnam are tied to that maritime focus. Japan wants to strengthen Vietnam’s economic resilience in case China retaliates against Vietnam’s maritime claims. Japan’s ODA has helped Vietnam build manufacturing capacity and reduce dependence on Chinese investment under Beijing’s Belt and Road Initiative. Japan has also pledged deeper cooperation on energy, critical minerals, semiconductors, supply chains and artificial intelligence. 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.
A recent proposal to jointly develop fast landing crafts suggests Japan supports Vietnam’s ability to hold and possibly retake offshore islands. Defense cooperation is expected to rise as Japan expands its OSA budget. On diplomacy, 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. Japan’s opposition to unilateral changes in the South China Sea supports its case for condemning China’s assertiveness in the East China Sea.
The article says Japan is not a great power and cannot defend Vietnam because of legal and material constraints, but Vietnam welcomes close maritime cooperation because it strengthens its multilateral foreign policy. 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 does not carry human-rights conditions or threaten the political authority of the Communist Party of Vietnam to the degree Western assistance can. A close relationship with Japan also prevents Tokyo from seeing Hanoi’s island reclamation activities as a threat to its sea lines of communication in the way it sees Beijing’s activities. Vietnam supports Japan becoming a permanent member of the United Nations Security Council, a position China opposes.
The article says bilateral ties will keep improving so long as Japan’s and Vietnam’s grand strategies remain aligned over the South China Sea. It says there is 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. Japan should consider supporting Vietnam’s continental objectives, including 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. The article says Japan’s assistance to Vietnam should address the maritime-continental dilemma and move beyond a purely maritime focus to lift Japan-Vietnam ties to an even higher ground.