Decolonisation, although a liberating process, often left newly independent nations grappling with political instability. Firstly, the artificial borders drawn by colonial powers failed to consider ethnic, religious, and tribal affiliations, leading to internal strife. Secondly, these nations lacked established administrative and governance mechanisms, resulting in power vacuums and the rise of authoritarian regimes. Thirdly, the Cold War superpowers often intervened in these states, supporting factions that aligned with their ideologies, thereby exacerbating tensions. Economic dependency on former colonisers also meant that many of these countries struggled to establish independent, robust economies, further complicating political stability.

The Spanish Civil War (1936-1939) can be viewed as a microcosm of the larger ideological battles that marked the 20th century. Pitting the Republicans, comprising communists, anarchists, and liberals, against the Nationalists, an alliance of conservatives, monarchists, and fascists, the war echoed the larger struggles between left-wing and right-wing ideologies prevalent across Europe. Moreover, international involvement, with Nazi Germany and Fascist Italy supporting the Nationalists and the USSR backing the Republicans, foreshadowed the looming WWII. The war highlighted the pervasive nature of ideological conflicts, transcending national boundaries and setting the stage for subsequent global confrontations.

Post-war reconstruction often provided an opportunity to reshape political governance in war-ravaged regions. With significant infrastructural and administrative damage, international bodies and influential nations stepped in to aid reconstruction. For instance, post-WWII Europe witnessed the Marshall Plan, where the US provided financial assistance, inadvertently fostering pro-Western sentiments. The Allied occupation of Germany and Japan aimed at democratization and de-militarisation, significantly influencing their political landscapes. In many regions, reconstruction became synonymous with nation-building, allowing dominant powers to instil governance models aligned with their ideologies and interests, often with long-term political repercussions.

The Middle East's significance in post-WWI geopolitics stems from both historical and pragmatic reasons. The dissolution of the Ottoman Empire, coupled with the Sykes-Picot Agreement, led to arbitrary territorial demarcations, disregarding ethnic and religious nuances. This sowed seeds of discord, with multiple ethnicities vying for dominance. Additionally, the discovery of vast oil reserves made the region economically invaluable. Western powers, keen on securing these resources, frequently intervened, leading to suspicions and mistrust. The establishment of Israel post-WWII further complicated matters, igniting Arab-Israeli tensions. Thus, the amalgamation of historical grievances, resource abundance, and external interventions positioned the Middle East at the heart of 20th-century geopolitical tensions.

The Cold War profoundly reshaped global alliances, leading to a clear bifurcation of power blocs. After WWII, the world gravitated towards two poles: the USA and the USSR, representing capitalist and communist ideologies respectively. The NATO, led by the US, stood as a collective defence against perceived Soviet aggression. Conversely, the USSR spearheaded the Warsaw Pact, consolidating its dominance over Eastern European nations. These alliances weren't merely military; they encapsulated economic and ideological collaboration, as seen with the Marshall Plan and Comecon. While the Cold War didn't lead to direct conflict between superpowers, their influence decisively shaped proxy wars, nuclear arms races, and global diplomacy.