The French encounter no resistance to their occupation of Mexico City.

In June 1863, a provisional government is chosen, and in October a delegation of Mexican conservatives invites Ferdinand Maximilian Joseph von Habsburg of Austria to accept the Mexican crown, all according to the plans of French emperor Napoleon III.

Maximilian is a well-intentioned monarch who accepts the crown believing that this act responds to the desire of a majority of Mexicans.

Before departing for Mexico, Maximilian signs an agreement with Napoleon III, under which Maximilian assumes the debts incurred for the upkeep of the French army in Mexico.

On June 12, 1864, the Emperor Maximilian I and his Belgian wife, Marie Charlotte Amelie Leopoldine, now called Empress Carlota, arrive in Mexico City.

The republican government under Juárez retreats to the far north.

Antonio López de Santa Anna's last political venture results in the sale of more Mexican territory.

In what is known in the United States as the Gadsden Purchase, ratified by the United States Congress in 1854, Santa Anna sells 77,692 square kilometers of land in southern New Mexico and Arizona for US$10 million.

This additional loss of territory alienates a large, reform-minded group of young Mexicans, who now conspired to oust Santa Anna.

The Mexican reform movement is inspired by the liberal political philosophies of European intellectuals, such as Jean-Jacques Rousseau, John Stuart Mill, and Pierre Joseph Proudhon.

Their views are adopted by a group of Mexican intellectuals who share a strong commitment to moralize Mexican politics.

The most outstanding member of the group is Benito Juárez, a Zapotec lawyer and politician.

Juarez and his cohorts go into exile in Louisiana, where they draw up the Plan of Ayutla in 1854 for the overthrow of Santa Anna.

As the plan gains broad-based support, the conspirators begin to return to Mexico.

In August 1855, in response to growing opposition, Santa Anna resigns for the last time.

A provisional government is installed under Juan Ruiz de Alvarez and the intellectuals of Ayutla; the ensuing period of liberal rule comes to be known as the Reform.

The Reform is touted as a Mexican version of the French Revolution.

Several laws, known collectively as the Reform Laws, abolish the fueros, curtail ecclesiastical property holdings, introduce a civil registry, and prohibit the church from charging exorbitant fees for administering the sacraments.

The Reform Laws polarize Mexican society along pro- and anticlerical lines at a time when delegates are preparing the constitution of 1857, as provided for in the Plan of Ayutla.

The new constitution is derived from that of 1824, but it reflects a more liberal vision of society through its incorporation of the Reform Laws.

It reaffirms the abolition of slavery, secularizes education, and guarantees basic civil liberties for all Mexicans.

Both the Reform Laws and the constitution, however, divide the political classes and set the stage for a civil war.

The civil war, commonly known as the War of the Reform, that engulfs Mexico between 1858 and 1861 brings to light the underlying conflicts that have been present in Mexican society since independence.

The conservative faction launches the Plan of Tacubaya and, with the support of the military and the clergy, dissolves congress and arrests Juárez.

Juárez escapes and establishes a "government in exile" in Queretaro (the liberals later move their capital to Veracruz).

The initial military advantage is held by the conservatives, who are better armed and have plentiful supplies, but by 1860 the situation is reversed.

The final battle takes place just before Christmas 1860.

The victorious liberal army enters Mexico City on January 1, 1861.

General Antonio López de Santa Anna returns from exile in 1853, and with the help of rebellious conservatives once again becomes Mexico’s ruler, declaring himself dictator for life with the title "Most Serene Highness".

As Mexico is willing to sell additional lands to the United States government, the Pierce administration sends American diplomat James Gadsden to negotiate a treaty whereby Mexico cedes a rectangular strip of about 29,640 square miles (76,760 kilometers) in the Mesilla Valley south of the Gila River for ten million dollars.

Southerners, whose Democratic party has put Franklin Pierce in office, plan on using the so-called Gadsden Purchase for a railway route to the Pacific.

Gadsden, a South Carolinian, is an ardent supporter of a southern railroad, but he envisions it being built to Charleston, South Carolina.

Gadsden is interested in this purchase since he has acquired shares of the railroad company that would unite Texas and California.

As originally envisioned, the purchase would have encompassed a much larger region, extending far enough south to include most of the current Mexican states of Coahuila, Chihuahua, Sonora, Nuevo Leon, and Tamaulipas as well as all of the Baja California peninsula.

These original boundaries had been opposed not only by the Mexican people, but also by anti-slavery U.S.

Senators who see the purchase as tantamount to the acquisition of more slave territory.

Outraged at the reduced size of the purchase, ...

Mexico had sold the large territory south of the Gila River and west of the Rio Grande, known to history as the Gadsden Purchase, for ten million dollars, but a very different treaty is finally ratified by the U.S. Senate and signed by President Franklin Pierce on June 24, 1854.

Although the agreement specified ten million dollars, the US Congress only agrees on seven million dollars ($163 million in 2006 dollars).

When the money finally arrives in Mexico City one million dollars ($23 million in 2006 dollars) has gone missing, thus resulting in a total of only six million dollars ($140 million in 2006 dollars).

The treaty includes a provision allowing the U.S. to build a transoceanic canal across the Isthmus of Tehuantepec, though this option will never be exercised.

With a few exceptions, such as the resolution of the Chamizal dispute, acquisition of land in this purchase defines the present boundaries of the continental United States.

Even the small strip of land that is ultimately acquired is enough to anger the Mexican people, who see Santa Anna's actions as yet another betrayal of their country and watch in dismay as he squanders the funds generated by the Purchase.

The Gadsden Purchase helps to end Santa Anna's political career.

Even Santa Anna's conservative allies, despite his generous payoffs to the military for loyalty, have had enough of him by 1855, when he loses Mexico’s presidential office for the fifth and final time, and a liberal, reformist government takes charge.

Santa Anna seeks refuge in Cuba.

As the extent of his corruption became known he is tried in absentia for treason and all his estates confiscated.

To replace him, a junta of representatives names as interim president a moderate liberal, General Martín Carrera, on from August 15.

On August 20, 1855, in agreement with the Plan de Ayutla, he calls elections for a constituent congress.

Under pressure from supporters and opponents of the Plan de Ayutla, he resigns in September, turning the office over to Rómulo Díaz de la Vega.

He then retires to private life in Mexico City.

After 22 days of Díaz de la Vega, a provisional government is installed under Álvarez and the intellectuals of Ayutla.

Álvarez, of mixed Indigenous and African heritage, rides into Mexico City in the company of a bodyguard of Indigenous fighters from the south.

His administration is short but brilliant: Ignacio Comonfort is Minister of War; Melchor Ocampo is foreign minister; Guillermo Prieto is Minister of the Treasury; and Benito Juárez is Minister of Justice.

In the 68 days that he governs, two measures are adopted that change the destiny of Mexico: the convocation of a constituent congress that would write the Constitution of 1857, and the abolition of military and ecclesiastical fueros (privileges).

The latter measure is the Ley Juárez.

One of Álvarez’s concerns throughout his career, both military and political, has been the return of lands to the Indigenous.

Urban life is foreign to Álvarez, and he does not like Mexico City.

Because of his mixed ancestry, his liberalism, and his leadership of Indigenous soldiers, Mexico City is not very hospitable to Álvarez, and there is conflict in his cabinet between supporters of Comonfort and Manuel Doblado.

For those reasons, and for reasons of health, Álvarez soon turns over the presidency to Comonfort, another supporter of liberal reforms.

Álvarez returns to Guerrero.

Comonfort, a moderate liberal who wishes to act a a stabilizing force between the radical conservatives, and the radical liberals (these are named puros, pure), takes office on December 11.

The ensuing period of liberal rule in Mexico comes to be known as the Reform, which is touted as a Mexican version of the French Revolution.

Several laws, known collectively as the Reform Laws, abolish the fueros, curtail ecclesiastical property holdings, introduce a civil registry, and prohibit the church from charging exorbitant fees for administering the sacraments.

The Reform Laws polarize Mexican society along pro- and anticlerical lines at a time when delegates are preparing the constitution of 1857, as provided for in the Plan of Ayutla.