|Emperor Le Dai Hanh|
Another common tactic is to lure the mighty enemies into their disadvantageous positions and counterattack or ambush them. Emperor Le Dai Hanh facing his mighty enemies-- the Song dynasty's troops--he tricked the advanced Song troops into a dead valley and ambushed them, killing their commander and defeating them in 981. In 1284-88, the Tran dynasty facing imminent invasion from Mongol army, under Mongke Khan and Kublai Khan, the Tran army avoided the open field battle with the Mongol army, but they had lured the enemies into their disadvantageous positions: swampland and tropical forests and counterattacked them in guerrila tactics to defeat them. Such a style of warfare was well practiced during the Vietnam War from 1964-75 against the US troops and their allies. Most American troops were killed by ambushes and explosive traps more than open field battle.
In conventional warfare, the Vietnamese like to use preemptive strike or surprised attack when the enemies were not in battle readiness. In 1418, Le Loi, a commander of Lam Son armies, launched a preemptive strike against the Ming dynasty troops, killing 300,000 of them and thwarted them completely. This tactic was also being used during the French war and the Vietnam War; in 1954, the Vietminh launched a surprised attack on French base at Dian Bien phu where the whole French troops surrendered and brought an end to the war. In 1968, the Vietcong troops simultaneously launched a surprised attack on all the US army positions across the country on the Vietnamese New Year Eve known as a "Tet Offensive." Such a preemptive strike made the US troops more nervous and confused since they could not use air support and heavy weapons against the Vietcong infiltrators in close ranges. Albeit both sides suffered the heavy loss, the Vietcong had made Americans psychologically felt intimidated by the power of the their underestimated enemies. Since then, the US military advance had been hailed, and the war fell into a stalemate that forced the US to withdraw its entire troops from Vietnam in 1973 before the collapse of its ally regime in 1975.
The Vietnamese invasion in Cambodia 1979 was well-designed and employed different tactics. As Cambodian army much smaller and weaker, Hanoi launched a surprised and overwhelmed attack akin to Hitler attacked Poland in 1939, rolling advanced columns from multiple directions simultaneously to deprive the enemies from reinforcement and to break their morale. The goal is to reach a super target--the capital city Phnom Penh, the command center--then spread their advanced columns toward different provincial towns. Battambang City was under the Vietnamese control on January 13 but most areas in the province were still under the Khmer Rouge control until the Khmer new Year. After conquering the country, the Vietnamese troops were well entrenched themselves in the fortified positions across the country, especially on the western part since most Khmer resistance forces concentrated on that area. It is quite different nature of war from 1970s war when Khmer Rouge had seized nearly 70 percent of the country, but during the Vietnamese occupation 1979-89 war, the Khmer Rouge and the other resistance forces retained control the country less than 5 percent mostly along Thai-Cambodia border.
Vietnam's steady growth of territory and power from tiny nation state to dominant power over Indochina has strongly alarmed its smaller neighbors, especially Cambodia which had already lost more than one third of its territory (Kampuchea Krom) to Vietnam in 19th century, and currently it still has struggled to liberate itself from Vietnam's political and economic control. In the past Vietnam had deployed its war tactics to defeat its bigger enemies and to conquer its neighbors. Now, Vietnam has deployed its economic and political tactics to conquer proper Cambodia through economic concession and political interference.