It began with an occupation in response to the Tampico Affair of April 9, 1914, where Mexican forces had detained nine American sailors, further worsened relations, and led to widespread anti-Americanism in Mexico.

The expansionist policies of US President James K. Polk, combined with the Mexican government's desire to retain control of Texas and Upper California, led to the outbreak of military conflict between the United States and Mexico in 1846.

[13] The decisive US victory led to Mexico ceding 55% of its territory to the United States[14] and a sense of animosity developing between the two nations.

After becoming president in March 1913, Woodrow Wilson withdrew US recognition from the government of Victoriano Huerta and began encouraging the great powers to follow suit.

A couple of months later, in October 1913, rebellions in the states of Chihuahua and Morelos led by Pancho Villa and Emiliano Zapata broke out after Huerta declared victory in a blatantly fraudulent election.

While awaiting authorization from the US Congress to carry out such action, Wilson was alerted to a delivery of weapons for General Victoriano Huerta due to arrive in the port on April 21 aboard the German-registered cargo steamer SS Ypiranga.

The weapons had actually been sourced by John Wesley De Kay, an American financier and businessman with large investments in Mexico, and a Russian arms dealer from Puebla, Leon Rasst, not the German government, as newspapers reported at the time.

The landing of the arms was blocked at Veracruz, but they were discharged a few weeks later in Puerto Mexico, a port controlled by Huerta at the time.

On the morning of April 21, 1914, warships of the United States Atlantic Fleet under the command of Rear Admiral Frank Friday Fletcher began preparations for the seizure of the Veracruz waterfront.

Maass then radioed a dispatch to General Aurelio Blanquet, Minister of War in Mexico City, of the American invasion.

[24] Arms were distributed to the population, who were largely untrained in the use of bolt-action rifles like the German-made Mausers and had trouble finding the correct ammunition.

[25] Although most of the regular troops retreated with Maass to Tejería, the liberated prisoners under the command of Lt. Col. Manuel Contreras, and some civilians, opposed the Americans as they made their way to the custom house.

A regiment led by Navy Captain E. A. Anderson advanced on the Naval Academy in parade-ground formation, making his men easy targets for the partisans barricaded inside.

[28]On April 26, Fletcher declared martial law, and started turning the occupation over to the American army under the command of General Frederick Funston.

[30] As an immediate reaction to the military invasion of Veracruz several anti-US riots broke out in Mexico, Argentina, Chile, Costa Rica, Ecuador, Guatemala, and Uruguay.

[31] US citizens were expelled from Mexican territory and some had to be accommodated in refugee campuses at New Orleans, Texas City, and San Diego.

[32] Even the British government was privately irritated, because they had previously agreed with Woodrow Wilson that the United States would not invade Mexico without prior warning.