Technological and communication advancements in the 20th century quickened integration of the human web. The proliferation of network technologies enhanced the flow of information and allowed people to travel further, faster, and more frequently. The rapid and easy flow of information and people reduced cultural and political diversity, in addition to transforming the character of science. Scientific advancements in medicine and public health decelerated urban death rates, and cities became sites of upward social mobility and better access to education, healthcare, clean water, electricity, and inexpensive food. Other significant characteristics of the 20th century include the transition to oil-based economies, which had an unprecedented impact on the environment and stimulated a long economic boom after 1950.

The cosmopolitan web faced disintegration in the 20th century via world wars and isolationist ideologies. World War I broke up empires and stimulated strong nationalist tendencies. Although a brief and partial recovery of capital and trade flows followed World War I, the stock market crash of 1929 reverberated throughout the world and prompted nations to adopt autarkic policies, authoritarianism, and expansionist tendencies. These dynamics led to four distinct conflicts—Japan versus China, Japan versus the US, Germany versus Britain and France, and Germany versus the USSR—which culminated in World War II.