Vietnam placed orders for $1 billion dollars in Russian weapons during a visit to the country last week by the Communist party boss, Nguyen Phu Trong.
The two sides committed themselves to developing their already close military ties.
Just as significantly, they pledged further cooperation over Vietnam’s oil and gas production in waters that are also claimed by an increasingly assertive China.
Russia is showing the breadth of its ambitions in Asia with a vast military exercise focused on eastern Siberia and said to involve up to 300,000 troops.
The mobilisation of such a force would have done justice to a major battle in WW2 and dwarfs the military power that any European country could put in the field.
The war games also put China and other Asian powers on notice that Moscow is once again a force to be reckoned with in the region.
China sent a significant but much smaller force to take part in the exercises, and President Putin and President Xi Jinping, are always keen to extol the warmth of their new friendship.
Both countries feel the need for closer ties given their respective struggles with the United States and its allies, in Asia and Europe.
However, whatever the short term calculations, China will be alert to longer term security risks posed by Moscow’s revived military capabilities on its border.
Vietnam, always alert to geopolitical opportunities, will be encouraged by President Putin’s ambitions.
Russia is already Vietnam’s biggest weapons supplier and has its eye on Vietnamese ports should it need to project naval power in the western Pacific.
Neither side gave any details of the latest arms deal. But Vietnam has been rapidly building up its naval capabilities in recent years, with Russian assistance, in an attempt to deter Chinese belligerence in the South China Sea.
The commitment of Russia to strengthen the role of its energy companies in Vietnam’s oil and gas industry also sends a clear message to China.
Beijing has scared off a number of European companies which were running joint ventures in Vietnamese waters that are also contested by China.
Russian companies, however, are less vulnerable to Chinese threats given the ostensibly friendly ties between Moscow and Beijing.
President Putin has also shown that he is prepared to back up his defence of Russian interests with military muscle.
China will therefore tend to turn a blind eye to Russian activities in its back-yard even as it asserts its right to the lion’s share of natural resources in the region.
Smart move by Vietnam which has had to back down in the face of Chinese threats in recent years to the detriment of its already ailing hydrocarbon industry.