The post-World War II taboo against acquiring territory through force or threat of force is being dismantled by a new generation of political leaders, spearheaded by Donald Trump’s unprecedented expansionist threats for a US president. Trump’s comments, combined with Russia’s aggression towards Ukraine, fuel a permissive environment that jeopardizes long-established borders and the international rules-based order that has been in place since the end of the war.

The norm, enshrined in article 2 of the 1945 UN Charter, states that all member states should refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state. While Trump’s threats have not yet materialized, there is a more tangible pursuit of expansionist goals elsewhere.

Experts argue that technology, climate change, and the demand for rare earth minerals exacerbate these expansionist tendencies. The US president’s imperialist outlook, such as his desire to acquire Greenland or make Canada America’s 51st state, reflects a policy reminiscent of the 19th century. Many worry how Trump’s actions and statements create a permissive space for territorial expansion.

It is clear that there has been a shift in the US’s approach from a historic “informal imperialism” that relied on coups and influence to Trump’s openness to annexation. This change in rhetoric has disrupted previous assumptions about America’s role in the world amid its declining power.

History serves as a reminder of the problems with expansionist policies. McKinley’s expansionist policies during the Spanish-American war were deeply contentious. Conquest, it is argued, is fundamentally incompatible with democracy, and the tenets of the liberal international order cannot survive without the norm against territorial conquest.

Source: https://www.theguardian.com/us-news/2025/mar/23/trump-expansionism-threatens-the-rules-based-order-in-place-since-second-world-war