Vietnam

Vietnam is the easternmost country on the Indochina Peninsula in Southeast Asia. With an estimated 90.5 million inhabitants as of 2014, it is the world's 13th-most populous country, and the eighth-most-populous Asian country. Vietnam was first officially adopted in 1802 by Emperor Gia Long, and was adopted again in 1945 with the founding of the Democratic Republic of Vietnam under Ho Chi Minh. The country is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and Malaysia across the South China Sea to the southeast. Its capital city has been Hanoi since the reunification of North and South Vietnam in 1976.

China
The Sino-Vietnamese War in 1979 resulted in a long period of lingering mistrust, as it rumbled on into the mid-1980's. The two sides clashed at sea in 1988 when China occupied its first holdings in the Spratly archipelago of the South China Sea, following its full control of the Paracels in 1974. More recently, in May 2014, China's placement of an oil rig in disputed waters for 10 weeks sparked anti-Chinese riots across Vietnam, amid China's historic claim to most of the Sea.

Vietnam's military accelerated a decade-long modernization drive in Hanoi's biggest arms buildup since the height of the Vietnam War by December 2015. Due to tensions in the South China Sea over rival claims to the Spratly and Paracel archipelagos, the ruling Communist Party's goal was to deter its northern neighbor from force as it placed key units, such as the elite Division 308, on high combat readiness in the mountainous north. In this quest, Vietnam purchased six advanced Kilo-class submarines from Russia, which patrolled the South China Sea. It also upgraded and expanded air defenses, obtaining early warning surveillance radars from Israel and advanced S-300 SAMs from Russia.

Economy
In Vietnam's arms buildup in the 2000's, increases in military spending outstripped its East Asian neighbors over the decade.

Some $5 trillion in ship-borne trade passes through the South China Sea every year, including most of the oil imported by China, Japan, and South Korea - the waters became a site of tension with China's holdings threatening many of the East Asian nations.