Since the completion of Vietnam's reunification in 1976, under the leadership of their new leader Le Thanh, they began to follow a path of external expansion, hoping to establish an "Indochina Federation" that would incorporate Cambodia and Laos into Vietnam's territory, so they sent troops to occupy Cambodia in 1978, and laos had been actually controlled by them before.
This is true not only for neighboring countries, but also for China, a former close friend, who has violated our borders, killed our border people, provoked trouble, desecrated our dignity and sovereignty, and repeatedly taught us, so there was a 79-year self-defense counterattack.
Why did Vietnam dare to be so unscrupulous at that time? The first is that Vietnam did indeed just defeat the United States and complete its reunification during that time, and it was inevitable that it would make a wrong judgment and make a wrong decision about the situation. Second, they had a strong ally behind them– the Soviet Union. The Soviets had been giving them military and military assistance, and had instigated a series of plans to invade Cambodia and control Laos that the Soviets had tacitly approved.
However, by the time of the self-defense counterattack in '79, the situation was completely different. They are not facing Laos and Cambodia, but China. What's more, we decided to launch this counterattack, not only to Vietnam, but more accurately, to the Soviet Union, and it is clear to everyone who is behind Vietnam. This counterattack, first, is to solve the problem, and we cannot let them form a north-south attack, and second, we cannot allow a huge regional force to appear in Southeast Asia. The third was to knock the Soviet Union.
Ms. Li Danhui of the Institute of Contemporary Chinese Graduate Studies of the Chinese Academy of Social Sciences put forward the fourth point in a program, saying that the battle was actually to prepare for reform and opening up. According to Ms. Li Danhui, at that time we were planning a big reform, and this reform could no longer rely on the Soviets, but only on the United States. Li Danhui said: At that time, Sino-US relations had actually come to a standstill (Sino-US diplomatic relations were established in 1972), and this war was to a certain extent to bring China-US relations closer together and tell the United States that we were containing the Soviet Union.
When the United States learned of this, of course, their statement could not be a clear support, but said that I am willing to help you supervise the Soviet Union. Li Danhui used the term "paramilitary alliance" to describe the relationship between the two sides at that time, that is, we had no worries. So what is the situation in the Soviet Union, they are military allies, what if the younger brother beats them? The reply of the ambassador to the Soviet Union was that at that time, the Soviets did not want to move at all, did not want to care, in fact they also wanted to adjust the relationship between the two sides. It was February, it was very cold, and they had chiseled the ice from the Ussuri River, the Heilongjiang River, and some lakes as a signal that they would not interfere.