The rise of nationalist movements within the Soviet Union during this period can be attributed to several key factors. Firstly, Gorbachev's policy of glasnost allowed previously suppressed national grievances to be openly discussed, which ignited nationalist sentiments. Secondly, the economic hardships and stagnation under the Soviet regime led many republics to seek greater autonomy or independence, believing they could manage their affairs more effectively. Additionally, the weakening of the Communist Party's control and the influence of democratic movements in Eastern Europe encouraged nationalist groups to push for independence. These movements gained momentum as the central Soviet authority weakened, playing a significant role in the eventual dissolution of the USSR.

During the late stages of the Cold War, particularly under Gorbachev's leadership, the Soviet Union sought to improve its economic relationships with the West. This shift was part of an attempt to integrate the Soviet economy into the global market and to gain access to Western technology and capital. Gorbachev's policies aimed to reduce tensions with the West, thereby opening up opportunities for increased trade and economic cooperation. However, these changes were not sufficient to overcome the deep-rooted economic problems within the USSR. While there was an increase in Western investment and joint ventures, the Soviet economy remained largely inefficient and was unable to fully capitalise on these new economic relationships.

The Strategic Defense Initiative (SDI), announced by President Reagan in 1983, significantly influenced Soviet foreign policy decisions. SDI, aimed at developing a space-based missile defense system, was perceived by the USSR as a major escalation in the arms race and a threat to the balance of power. The Soviet leadership feared that SDI would give the United States a strategic advantage and undermine the concept of Mutually Assured Destruction (MAD), which had been a deterrent against nuclear war. As a result, the USSR increased its own military spending to keep pace, further straining its already troubled economy. This, in turn, pressured Soviet leaders to seek de-escalation and arms reduction talks with the United States, leading to agreements such as the INF Treaty and ultimately influencing the trajectory of the Cold War's conclusion.

The Chernobyl disaster in 1986 was a critical event in the decline of the Soviet Union. This nuclear accident not only highlighted the inefficiencies and failures of the Soviet system but also exposed the limitations of the government's ability to manage crises. The disaster and its mishandling severely undermined public trust in the government, especially as the scale of the catastrophe and the associated risks were initially downplayed and concealed from the public and the international community. The Chernobyl incident, therefore, not only had dire environmental and health consequences but also acted as a catalyst for increased public dissatisfaction and scepticism towards the Soviet government, hastening its eventual collapse.

The Soviet-Afghan War (1979-1989) significantly strained the USSR both economically and politically, impacting its Cold War dynamics. The conflict, often referred to as the USSR's "Vietnam War", was a costly endeavour, draining valuable resources and funds that could have been used to bolster the Soviet economy. The war also damaged the USSR's international reputation, leading to widespread condemnation and contributing to its isolation on the global stage. Domestically, the war caused significant casualties and disillusionment among the Soviet populace, weakening the government's legitimacy. This demoralisation, coupled with the economic drain, contributed to the weakening of the Soviet Union in its Cold War confrontation with the West.