20th Century Revolutions: Characteristics, Types, and Waves

The 20th century was very rich in various revolutionary events, exceeding the number of revolutions of the 19th century. The revolutionary process had a big impact on the World System and significantly changed its entire configuration. Revolutions created Communist states, wiped out colonial empires and finally destroyed the world Communist camp. Despite many studies, there remain gaps in theoretical approaches, especially typologies, and a lack of comprehensive qualitative and quantitative analyses covering the 20th century as a whole. This article offers such analyses, develops aspects of the theory of revolution tailored to the 20th century, proposes a novel typology including the concept of analogues of revolution, and introduces a new approach to defining revolutionary waves. The main research question is to identify the number and contents of revolutionary waves in the 20th century using a clear set of scientific criteria.

Theoretical framework: Numerous studies address 20th-century revolutions (e.g., Goldstone 2001; Sanderson 2016; Lawson 2016; Grinin et al. 2016; Shults 2016; Ardalan 2020). Yet typological gaps persist, and scholars often do not situate revolutions within the spectrum of other regime-change events. To address this, the authors develop the term "analogue of revolution" (Grinin and Grinin, 2020) for events close to revolutions in significance and mass mobilization but differing in the mechanism of government change (elections or coups). The article engages with debates on revolutionary waves, noting that existing theories struggle to explain them (Beck, 2011, 2014; Lawson, 2015). Prior typological distinctions include classic vs. other revolutions; revolutions in developed vs. developing countries; Western vs. Eastern/Third World; and European vs. non-European empires (Von Laue 1964; Tucker 1969; Huntington 1968, 1986; Foran 2005; Hobsbawm 1996). The authors present an original database of 20th-century revolutionary events (Table S1), enabling both qualitative and quantitative analyses over decades and 5-year periods, and extend earlier preliminary work in Russian (Grinin and Grinin, 2020).

Study design: Methods and materials. The study proceeds in three phases: (1) compare revolutions of the 20th and 19th centuries using generalizing works on 19th-century revolutions (e.g., Tilly 1996; Beck 2011; Grinin 2018, 2019; Zinkina et al. 2019) and a newly compiled database of 20th-century revolutionary events (Supplementary Table S1). (2) Identify characteristics, demands, and outcomes of 20th-century revolutions to classify them by type (objectives and ideologies). (3) Use world-systemic causes identified and the developed classification to delineate the main revolutionary waves of the 20th century. Criteria for waves include: a shared world-systemic cause; a non-trivial number of revolutions (minimum 4–5 in medium/large countries, more in small states); a limited time interval (≤10 years between start of first and last event); and only one wave per period. The database enumerates 125 revolutionary events with attributes such as kind (revolution vs. analogue), type/subtype, timing, and clustering into waves. Quantitative analyses include distributions by decade and 5-year periods, ratios of kinds and types, and per-wave compositions.

- Differences from 19th-century revolutions: the 20th century saw heightened aspirations for radical social equality (including abolition of private property), a shift of revolutionary activity from the World System core to semi-periphery/periphery, emergence and diffusion of new types (communist, anti-communist, national-socialist/right-wing), and an increased role of guerrilla warfare. - External drivers intensified: stronger links between revolutions and wars; geopolitical factors (world wars, collapse of empires, ideological confrontation fascism vs. communism, later communism vs. capitalism); and, in later decades, globalization effects. - Scope: 125 revolutionary events (revolutions and analogues) in the 20th century, nearly tripling the estimated 40–45 classic revolutions of the 19th century. - Typology (by objectives/ideologies) identified major types: democratic (anti-monarchic, anti-dictatorial), social, communist (incl. African-Socialist), anti-communist, power-modernist, national and national-liberation, national-socialist/right-wing, religious, and other confessional/ethno-political variants. National and national-liberation events predominate when combined; democratic and communist follow. - Analogues of revolution: Concept formalized to capture events effecting regime and structural change via coups or elections with mass mobilization before/after the change. Of 125 events, 36 were analogues (~30%), with a revolutions-to-analogues ratio of ~2.5:1. Among analogues, military coups were most common (20/36, >55%); some occurred via elections (~14%). Analogues appear prominently in the 1930s and 1960s–1970s. - Waves: Five revolutionary waves identified meeting the authors’ criteria: 1) 1905–1911 (8 events): driven by modernization and resistance to dependence; key cases Russia, Turkey, Persia, China, Mexico; dominated by democratic/social and power-modernist types. 2) 1917–1923 (17 events): tied to WWI outcomes and collapse of empires; though the Russian communist revolution is pivotal, most events were national/national-liberation (10/17, 59%). 3) 1930–1938 (11 events): associated with the Great Depression and rise of right-wing regimes; includes Spain 1931–1939 and Nazi Germany’s analogue; notable presence of national-socialist/right-wing events alongside democratic/social types. 4) 1943–1949 (15 events): outcomes of WWII; strong diffusion of communist ideology; many Eastern European cases were analogues supported by occupation contexts; majority communist type (10/15, 67%), with national-liberation components in places like Yugoslavia and Vietnam. 5) 1989–1996 (24 events): anti-communist revolutions in Eastern Europe and parts of the USSR sphere; many were peaceful (Velvet); nonetheless, more events were national/national-liberation (10) than anti-communist (8); involved state dissolutions (USSR, Yugoslavia) with ethno-nationalist dynamics. - Distribution across waves: 75 events (60%) occurred within waves (1st: 8; 2nd: 17; 3rd: 11; 4th: 15; 5th: 24); 50 occurred outside waves. The 2nd, 4th, and 5th waves had the most events and broad world impact. - Overall, revolutionary activity shifted geographically to the semi-periphery and periphery, with guerrilla warfare common and the role of revolutions as drivers of global progress declining over the century.

The study addresses the main research question by delineating five distinct revolutionary waves in the 20th century based on explicit world-systemic criteria and by quantifying their composition. It shows that waves arise from powerful system-level shocks (world wars, global economic crises, major regime failures) that catalyze simultaneous or closely timed revolutionary processes across countries. Classification by objectives/ideologies reveals that national and national-liberation events dominated several waves, even when public perception emphasizes other types (e.g., communist in 1917–1923 and anti-communist in 1989–1996). The introduction and operationalization of "analogues of revolution" clarifies patterns in periods and regions where regime-changing transformations occurred without classic mass-overthrow sequences, notably through military coups or electoral pathways coupled with mass mobilization. The findings underscore the growing extra-domestic determinants of revolution in the 20th century, including war linkages, geopolitical realignments, and globalization, and highlight the shift of revolutionary epicenters from the core to semi-periphery/periphery. Together, these results refine revolutionary theory by integrating typology, systemic causation, and wave dynamics, offering a more comprehensive account of the 20th-century revolutionary process.

The article identifies major characteristics distinguishing 20th- from 19th-century revolutions, including the shift toward the semi-periphery/periphery, increased guerrilla warfare, and the rise of new types (communist and later anti-communist). It introduces a new typology of revolutionary events and the concept of analogues of revolution to account for regime-transforming processes achieved via coups or elections with mass mobilization before/after the change. Using a curated database, the study performs qualitative and quantitative analyses to map five revolutionary waves (1905–1911; 1917–1923; 1930–1938; 1943–1949; 1989–1996), detailing their dominant types and system-level triggers. National and national-liberation events prevail overall, followed by democratic and communist types; analogues comprise about 30% of events and are crucial to understanding mid-century and decolonization-era dynamics. The study suggests that revolutions, particularly deep social revolutions in less prepared societies, are costly and risky pathways to transformation, with authoritarian regimes founded in such revolutions tending to be durable. Future research should extend the taxonomy to incorporate spatial dimensions and regional specificities, and further refine wave criteria and datasets.

The taxonomy presented is incomplete and should be expanded to account for spatial and regional variations (e.g., distinctive trajectories in South/Central America). The delineation of waves, while based on explicit criteria, involves subjective judgments about thresholds and world impact. Data limitations may exist despite the constructed database; the classification of events into types and the designation of analogues can be sensitive to definitional choices. The study focuses on the 20th century and does not fully integrate non-revolutionary transformative processes (e.g., reforms) beyond framing analogues.