Despite President Woodrow Wilson being a primary architect of the League of Nations, the United States Senate refused to ratify the Treaty of Versailles, thereby preventing the US from joining the League. This decision was influenced by concerns over compromising US sovereignty and the desire for a more isolationist foreign policy. The absence of the United States, a major world power, considerably weakened the League’s authority and credibility. Without the US's political, economic, and military weight, the League struggled to enforce its mandates and prevent aggressive actions of certain countries. This limitation became evident when the League failed to halt the actions of Italy, Japan, and Germany in the 1930s.

The Treaty of Lausanne, signed in 1923, is considered more successful in ensuring regional stability because it effectively replaced the harsher Treaty of Sèvres, which was largely seen as unrealistic and too punitive on the Ottoman Empire. The Treaty of Lausanne acknowledged the sovereignty and territorial integrity of the newly established Republic of Turkey. By doing so, it eliminated the majority of minority issues, settled border disputes, and led to population exchanges between Greece and Turkey. This ensured that potential flashpoints were considerably reduced. Unlike other post-war treaties, which often left lingering discontent, Lausanne was more balanced and considerate, leading to a prolonged period of peace in the region.

The League of Nations took an active role in addressing global health issues, recognising that health was intrinsically linked to peace and security. One of its agencies, the Health Organisation, conducted studies and coordinated international responses to combat epidemics. It was instrumental in curbing diseases like malaria, typhus, and yellow fever. The League also organised international health conferences, bringing together professionals to share knowledge and best practices. Additionally, it sought to standardise drugs and medical practices. Even though the League had numerous shortcomings in political matters, its contributions to global health were commendable and laid the groundwork for future international health collaborations.

The Potsdam Conference of 1945, while significant in shaping the post-WWII order, faced criticism on several fronts. First, the conference's decisions, primarily influenced by the Big Three (US, UK, USSR), marginalised smaller Allied nations. Second, the ambiguity regarding the post-war treatment of Germany left unresolved tensions, especially concerning reparations and de-industrialisation. Furthermore, critics argue that the Potsdam Conference entrenched the Cold War's ideological division by endorsing different governance forms for East and West Germany. The disagreements over Poland's western border and the lack of clarity on liberated European territories’ governance also drew criticism, indicating that the conference left more questions than answers.

The Treaty of Trianon, signed in 1920, had a profound effect on Hungary in the interwar years. As a direct result, Hungary lost about two-thirds of its territory and nearly 60% of its population to neighbouring states. This significantly reduced its economic and military potential. The loss of key industrial regions and resources strained the nation’s economy. Moreover, many ethnic Hungarians found themselves in foreign territories, leading to potential minority issues. The treaty's terms left Hungary in a state of national trauma, which, combined with the global economic downturn, led to political instability. Such conditions eventually paved the way for right-wing and authoritarian rule, especially under Admiral Miklós Horthy.