On the last day of 2013 Vietnam received its first submarine, a Russian made Kilo class boat. This is the first of six Kilos, which were ordered in 2009 and cost $2.1 billion. The Kilos are based at Cam Ranh Bay, a deep water port developed by the United States during the 1960s and has since then been a major shipping and ship maintenance facility. The Russian fleet has used the facilities there for three decades.
The Kilos weigh 2,300 tons (surface displacement), have six torpedo tubes, and a crew of 57. They are quiet and can travel about 700 kilometers under water at a quiet speed of about five kilometers an hour. Kilos carry 18 torpedoes or SS-N-27 anti-ship missiles (with a range of 300 kilometers and launched underwater from the torpedo tubes). The combination of quietness and cruise missiles makes Kilo very dangerous to surface ships.
India, China, and Iran have also bought Kilos. China is building its own unlicensed version of the Kilo (the Type 41 Song class). Considering the low price, it appears that the Vietnamese boats do not have AIP (Air Independent Propulsion), which allows non-nuclear boats to stay underwater for weeks at a time.
The Kilos are the first subs the Vietnamese Navy has ever had are were obtained to provide some defense against growing Chinese naval power.