Victoriano Huerta in the context of "Liberation Army of the South"

The military history of Mexico encompasses armed conflicts within that nation's territory, dating from before the arrival of Europeans in 1519 to the present era. Mexican military history is replete with small-scale revolts, foreign invasions, civil wars, indigenous uprisings, and coups d'état by disgruntled military leaders. Mexico's colonial-era military was not established until the eighteenth century. After the Spanish conquest of the Aztec Empire in the early sixteenth century, the Spanish crown did not establish on a standing military, but the crown responded to the external threat of a British invasion by creating a standing military for the first time following the Seven Years' War (1756–63). The regular army units and militias had a short history when in the early 19th century, the unstable situation in Spain with the Napoleonic invasion gave rise to an insurgency for independence, propelled by militarily untrained men fighting for the independence of Mexico. The Mexican War of Independence (1810–21) saw royalist and insurgent armies battling to a stalemate in 1820. That stalemate ended with the royalist military officer turned insurgent, Agustín de Iturbide persuading the guerrilla leader of the insurgency, Vicente Guerrero, to join in a unified movement for independence, forming the Army of the Three Guarantees. The royalist military had to decide whether to support newly independent Mexico. With the collapse of the Spanish state and the establishment of first a monarchy under Iturbide and then a republic, the state was a weak institution. The Roman Catholic Church and the military weathered independence better. Military men dominated Mexico's nineteenth-century history, most particularly General Antonio López de Santa Anna, under whom the Mexican military were defeated by Texas insurgents for independence in 1836 and then the U.S. invasion of Mexico (1846–48). With the overthrow of Santa Anna in 1855 and the installation of a government of political liberals, Mexico briefly had civilian heads of state. The Liberal Reforms that were instituted by Benito Juárez sought to curtail the power of the military and the church and wrote a new constitution in 1857 enshrining these principles. Conservatives comprised large landowners, the Catholic Church, and most of the regular army revolted against the Liberals, fighting a civil war. The Conservative military lost on the battlefield. But Conservatives sought another solution, supporting the French intervention in Mexico (1862–65). The Mexican army loyal to the liberal republic were unable to stop the French army's invasion, briefly halting it with a victory at Puebla on 5 May 1862. Mexican Conservatives supported the installation of Maximilian Hapsburg as Emperor of Mexico, propped up by the French and Mexican armies. With the military aid of the U.S. flowing to the republican government in exile of Juárez, the French withdrew its military supporting the monarchy and Maximilian was caught and executed. The Mexican army that emerged in the wake of the French Intervention was young and battle tested, not part of the military tradition dating to the colonial and early independence eras.

Liberal General Porfirio Díaz was part of the new Mexican military, a hero of the Mexican victory over the French on Cinco de Mayo 1862. He revolted against the civilian liberal government in 1876, and remained continuously in the presidency from 1880 to 1911. Over the course of his presidency, Díaz began professionalizing the army that had emerged. By the time he turned 80 years old in 1910, the Mexican military was an aging, largely ineffective fighting force. When revolts broke out in 1910–11 against his regime, a rebel forces scored decisive victories over the Federal Army in the opening chapter of the Mexican Revolution (1910–1920). Díaz resigned in May 1911, but Francisco I. Madero, on whose political behalf rebels rose against Díaz, demobilized the rebel forces and kept the Federal Army in place. "This single decision cost [Madero] the presidency and his life." Army General Victoriano Huerta seized the presidency of Madero in 1913, with Madero murdered in the coup d'état. Civil war broke out in the wake of the coup. Huerta's Federal Army racked up one defeat after another by the revolutionary armies, with Huerta resigning in 1914. The Federal Army ceased to exist. A new generation of fighting men, most of whom with no formal military training but were natural soldiers, now fought against each other in a civil war of the winners. The Constitutionalist Army under the civilian leadership of Venustiano Carranza and the military leadership of General Álvaro Obregón were the victors in 1915. The revolutionary military men were to continue to dominate Mexico's postrevolutionary period, but the military men who became presidents of Mexico brought the military under civilian control, systematically reining in the power of the military and professionalizing the force. The Mexican military has been under civilian government control with no President of Mexico being military generals since 1946. The fact of Mexico's civilian control of the military is in contrast the situation in many other countries in Latin America.

The Federal Army (Spanish: Ejército Federal), also known as the Federales (English: Federals) in popular culture, was the army of Mexico from 1876 to 1914 during the Porfiriato, the rule of President Porfirio Díaz, and during the presidencies of Francisco I. Madero and Victoriano Huerta. Under President Díaz, a military hero against the French Intervention in Mexico, the senior officers of the Federal Army had served in long-ago conflicts; at the time of the outbreak of the Mexican Revolution, most were old men, incapable of leading troops on the battlefield. When the rebellions broke out against Díaz following fraudulent elections in 1910, the Federal Army was incapable of responding.

Although revolutionary fighters helped bring Francisco I. Madero to power, Madero retained the Federal Army rather than the revolutionaries. Madero used the Federal Army to suppress rebellions against his government by Pascual Orozco and Emiliano Zapata. Madero placed General Victoriano Huerta as interim commander of the military during the Ten Tragic Days of February 1913 to defend his government. Huerta changed sides and ousted Madero's government. Rebellions broke out against Huerta's regime. When revolutionary armies succeeded in ousting Huerta in July 1914, the Federal Army ceased to exist as an entity, with the signing of the Teoloyucan Treaties.

The Constitutionalists (Spanish: Constitucionalistas) were a faction in the Mexican Revolution (1910–1920). They were formed in 1914 as a response to the assassination of Francisco Madero and Victoriano Huerta's coup d'etat. Also known as Carrancistas, taking that name from their leader, Venustiano Carranza the governor of Coahuila. The Constitutionalists played the leading role in defeating the Mexican Federal Army on the battlefield. Carranza, a centrist liberal attracted Mexicans across various political ideologies to the Constitutionalist cause. Constitutionalists consisted of mainly middle-class urbanites, liberals, and intellectuals who desired a democratic constitution under the guidelines "Mexico for Mexicans" and Mexican nationalism. Their support for democracy in Mexico caught the attention of the United States, who aided their cause. In 1914, the United States occupied Mexico's largest port in Veracruz in an attempt to starve Huerta's government of customs revenue. They crafted and enforced the Mexican Constitution of 1917 which remains in force today. Following the defeat of General Huerta, the Constitutionalists outmaneuvered their former revolutionary allies Emiliano Zapata and Pancho Villa becoming the victorious faction of the Mexican Revolution. However the Constitutionalists were divided amongst themselves and Carranza was assassinated in 1920. He was succeeded by General Álvaro Obregón who began enforcing the 1917 constitution and calming revolutionary tensions. His assassination and the subsequent power vacuum this created spurred his successor, Plutarco Elías Calles to create the National Revolutionary Party (PNR) which would hold uninterrupted political power in Mexico until 2000.

José Venustiano Carranza de la Garza (Spanish pronunciation: [benusˈtjano kaˈransa ðe la ˈɣaɾsa]; 29 December 1859 – 21 May 1920), known as Venustiano Carranza, was a Mexican land owner, revolutionary, and politician who served as the 44th President of Mexico from 1917 until his assassination in 1920, during the Mexican Revolution. He was previously Mexico's de facto head of state as Primer Jefe (Spanish: "First Chief") of the Constitutionalist faction from 1914 to 1917, and previously served as a senator and governor for Coahuila. He played the leading role in drafting the Constitution of 1917 and maintained Mexican neutrality in World War I.

Born in Coahuila to a prominent landowning family, he served as a senator for his state during the Porfiriato, appointed by President and dictator Porfirio Díaz. After becoming alienated from Díaz, he supported the Liberal Francisco Madero's challenge to Díaz during the 1910 presidential election. Madero was defeated in a sham election and imprisoned. Madero ordered an overthrow of the government, sparking the Mexican Revolution, and Díaz resigned in May 1911. As president, Madero appointed Carranza as the governor of Coahuila. When Madero was murdered during the counter-revolutionary Ten Tragic Days coup in February 1913, Carranza drew up the Plan of Guadalupe, a political strategy to oust Madero's usurper, General Victoriano Huerta. Carranza organized militias loyal to his state and allied northern states in Mexico into a professional army, the Constitutional Army, to oppose Huerta. The Constitutionalists defeated Huerta's Federal Army and Huerta was ousted in July 1914. Carranza did not assume the title of provisional president of Mexico, as called for in his Plan of Guadalupe, since it would have prevented his running for constitutional president once elections were held. Furthermore his government in this period was in a pre-constitutional, extralegal state, to which both his best generals, Álvaro Obregón and Pancho Villa, objected to Carranza's seizure of the national presidency.

The Constitutional Army (Spanish: Ejército constitucional), also known as the Constitutionalist Army (Spanish: Ejército constitucionalista), was the army that fought against the Federal Army, and later, against the Villistas and Zapatistas during the Mexican Revolution. It was formed in March 1913 by Venustiano Carranza, so-called "First-Chief" of the army, as a response to the murder of President Francisco I. Madero and Vice President José María Pino Suárez by Victoriano Huerta during La Decena Trágica (Ten Tragic Days) of 1913, and the resulting usurpation of presidential power by Huerta.

Carranza had a few military forces on which he could rely for loyalty. He had the theoretical support of Pancho Villa and Emiliano Zapata, but they soon turned against the Constitutionalists after Huerta's defeat in 1914.

Álvaro Obregón Salido (Spanish pronunciation: [ˈalβaɾo oβɾeˈɣon]; 19 February 1880 – 17 July 1928) was a Mexican general, inventor and politician who served as the 46th President of Mexico from 1920 to 1924. Obregón was re-elected to the presidency in 1928 but was assassinated before he could take office.

Born in Navojoa, Sonora, Obregón joined the Revolution after the February 1913 coup d'état that brought General Victoriano Huerta to the presidency. Obregón supported Sonora's decision to follow Governor Venustiano Carranza as leader of the northern revolutionary coalition, the Constitutionalist Army, against the Huerta regime. Obregón quickly became the Constitutionalist Army's most prominent general, along with Pancho Villa. Carranza appointed Obregón commander of the revolutionary forces in northwestern Mexico. The Constitutionalists defeated Huerta in July 1914, and the Federal Army dissolved in August. In 1915, the revolution entered a new phase of civil war between the Conventionists led by Emiliano Zapata and Villa versus Obregón and Carranza. Obregón was made leader of the Constitutionalist army and defeated Villa, but lost his right arm. In 1917, the Constitution of Mexico went into effect and the Conventionists forces were quickly getting defeated by Obregón and the Constitutionalist Army. Carranza stepped down from the presidency and designated Ignacio Bonillas to succeed him. Obregón and other Sonoran generals Plutarco Elías Calles and Adolfo de la Huerta ousted Bonillas and Carranza under the Plan of Agua Prieta. Obregón was elected to the presidency in 1920 with overwhelming popular support.

Pascual Orozco Vázquez, Jr. (in contemporary documents, sometimes spelled "Oroszco") (28 January 1882 – 30 August 1915) was a Mexican revolutionary leader and general who rose up to support Francisco I. Madero in late 1910 to depose long-time president and dictator Porfirio Díaz (whose eponymous era lasted from 1876 to 1911). Orozco was a natural military leader whose victory over the Federal Army at Ciudad Juárez was a key factor in forcing Díaz to resign in May 1911. Following Díaz's resignation and the democratic election of Madero in November 1911, Orozco served Madero as leader of the state militia in Chihuahua, a paltry reward for his service in the Mexican Revolution. Orozco revolted against the Madero government 16 months later, issuing the Plan Orozquista in March 1912. It was a serious revolt which the Federal Army struggled to suppress. When Victoriano Huerta led a coup d'état against Madero in February 1913 during which Madero was murdered, Orozco joined the Huerta regime. Orozco's revolt against Madero somewhat tarnished his revolutionary reputation, but his subsequent support of Huerta compounded the repugnance against him.

The Ten Tragic Days (Spanish: La Decena Trágica) is the name given to the multi-day coup d'état during the Mexican Revolution in Mexico City. It was staged by opponents of Francisco I. Madero, the democratically elected president of Mexico, between 9–19 February 1913. The coup instigated a second phase of the Mexican Revolution, after dictator Porfirio Díaz had been ousted and replaced in elections by Francisco I. Madero. The coup was carried out by general Victoriano Huerta and supporters of the old regime, with support from the United States, especially U.S. ambassador Henry Lane Wilson.

In the ten days of violence, the aim was to "create the illusion of chaos necessary to induce Madero to step down" from the presidency. Rebels led by General Félix Díaz, nephew of ex-president Porfirio Díaz, and General Bernardo Reyes escaped from jail and rallied forces to overthrow President Francisco I. Madero. The coup was strongly supported by U.S. Ambassador to Mexico, Henry Lane Wilson, who was implacably opposed to Madero. Madero had retained the Mexican Federal Army after rebels had forced the resignation of President Porfirio Díaz. The head of the Mexican Federal Army, General Victoriano Huerta, ostensibly the defender of the Madero government, defected to the rebels, who sought the return of the old political order. On 18 February the sitting president and vice president were captured by rebel General Aureliano Blanquet, effectively ending Madero's presidency. On 19 February, a dispute between General Díaz and General Huerta about who should head the provisional government was resolved by Ambassador Wilson mediating between the two in an in-person meeting at the U.S. embassy. They formalized an agreement known as the Pact of the Embassy.