Habsburg Maximilian became Emperor of Mexico in 1863. At the time of his coronation, battles were still raging between the republicans and the monarchists, so his rule was solidified with the help of 8,000 Austrian, Hungarian, Czech, and Polish volunteers alongside the French and Belgian armies.

The overseas adventure was particularly enticing for many because it seemed within reach that Mexico might have a Hungarian empress. Childless Maximilian named the grandchildren of Mexico's first emperor, Agustín de Iturbide, as his heirs. Consequently, Prince Salvador de Iturbide traveled to Europe to find a bride and met his future wife, Baroness Gizella Mikos, in Hungary. They married in 1871, with their wedding held at the Mikosszéplak castle.

Meanwhile, Benito Juárez, the republican president of Zapotec origin, also had Hungarian ties. His daughter-in-law was Maria Clerian, fathered by Gustav Remellay, a Hungarian hussar colonel and writer, in Novi Sad (now in Serbia).

The Austrian-Hungarian corps’ hussars were nicknamed "Red Devils" by the Mexicans because of their blood-red trousers and the previously unknown and fearsome tactics they employed. The hussars were led by Colonel Count Alfonz Kodolits, with notable aides-de-camp such as Baron Guido Czillich and Count Karl Khevenhüller.

Though the legion's original role was to protect the imperial couple, from 1864, they actively participated in battles. Out of 55 battles fought by the Austrian-Hungarian legion, they lost only nine.

When General Porfirio Díaz, a future republican president, was captured during the siege of Oaxaca and imprisoned in a Carmelite monastery converted into a jail in Puebla, he was freed by Hungarian Lieutenant János Csizmadia on September 20, 1865, to save him from execution.

This daring escape was made possible because the Hungarian guards, tasked with Díaz's custody, got drunk and distracted themselves with dances performed by Roma musicians they had brought along. These dances, known in Hungarian as “Máriás,” influenced not only the musical style of mariachi but also its etymology. This connection is reflected in the saying: “vive como húngaro” (“live like a Hungarian”).

In 1867, with Ede Pawlowsky serving as the military commander of Mexico City, Hungarian engineer Pál Sarlay redesigned the central park of the capital and initiated the transformation of the Zócalo into the world’s largest square.

On the republican side, approximately 500 Hungarians fought. Among them were the Hungarian soldiers of the Chicago Lincoln Riflemen, the 21st New York Infantry Regiment founded by Kornél Fornet, and the 39th New York Volunteer Infantry Regiment (the Italian Garibaldi Guards), which included three Hungarian-speaking companies. Most of these troops had previously fought against the Habsburgs in the Hungarian Revolution of 1848–49.

Colonel István Zákány Csala also fought as a leader of the republican forces. Initially commanding the 3rd Infantry Regiment, he later became the chief of staff of the western armies. He was the one who captured Maximilian during the Battle of Cerro de las Campanas and handed him over to the execution squad.

Dr. Ede Szenger, a physician from Pest, was also present at the fatal execution. Minutes later, he supervised the autopsy and embalming of the emperor.

Dr. Szenger remained in Mexico for over a decade, practicing as a private doctor in San Luis de Potosí, where he founded the medical organization Sociedad Médica Potosina. He eventually returned to Budapest as a Knight of the Order of Guadalupe, using his savings to construct several buildings. One of these, located at Király Street 42, was funded by the sale of Aztec and Mayan treasures to the Hungarian Ethnographic Museum.