The trip could offer an opportunity to show that Russia has international supporters.
Russian President Vladimir Putin meets Vietnamese leaders in Hanoi on Thursday after signing a mutual defence deal with North Korea.
AFP looks at the background of the visit and what the two sides hope to achieve.
Why is Putin going to Hanoi?
Vietnam and Russia have close ties going back to the 1950s, but Hanoi is not likely to give Putin the public pledge of "full support" for Ukraine that he received from North Korean leader Kim Jong Un.
The Southeast Asian manufacturing powerhouse has for years carefully avoided allying too closely with any major power -- the so-called "bamboo diplomacy" approach of seeking strength through flexibility.
Both US President Joe Biden and China's Xi Jinping have visited in recent months to deepen relations.
But receiving Putin -- under sanctions and seen as a pariah by much of the world -- will be "a test of how far Hanoi's multi-directional hedge can go and still be accepted by other major powers", said Huong Le Thu, deputy director of the Asia Program at the International Crisis Group.
For the Russian leader, the trip could offer an opportunity to show that he has international supporters, Thu said.
What's their history?
The former Soviet Union was one of the first countries to recognise the Vietnamese government of Ho Chi Minh and establish diplomatic ties, in 1950.
Some 50,000 Vietnamese studied in Soviet universities up to 1991, and successive Vietnamese governments have been heavily reliant on arms supplied by the Kremlin for decades.
During the war with the United States, the Soviet Union provided its fellow communists in Vietnam with jet fighters, missiles, helicopters, and tanks as well as nearly 11,000 soldiers, according to Vietnam's Army newspaper.
The ties endured even after the collapse of the Soviet Union -- Russia accounted for more than 80 percent of Vietnam's arms imports between 1995 and 2023, according to data from the Stockholm International Peace Research Institute (SIPRI).
Moscow also used Vietnam's strategic Cam Ranh Bay in the South China Sea as its military base in the Asia Pacific for more than two decades until 2002.
The two upgraded ties to a comprehensive strategic partnership, Hanoi's highest level, in 2012. Australia, China, India, Japan, South Korea, and the United States also share top-level ties with Vietnam.
What will they discuss?
Russian officials say the talks will focus on trade, education, and energy issues, in particular, how Moscow can help Vietnam transition to clean power.
But analysts say arms exports, the war in Ukraine, and Moscow's promised support for Hanoi to join the BRICS group of emerging economies will also be on the table.
Vietnam's arms imports from Russia have dropped off in recent years amid international sanctions over the Ukraine invasion.
Carl Thayer, emeritus professor of politics at Australia's University of New South Wales, said that behind closed doors, the two sides will likely work on ways to do business without falling foul of Western sanctions.
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