The Flag of the United Mexican States or Mexico is a vertical tricolor of green, white, and red with the national coat of arms charged in the center of the white stripe. While the meaning of the colors has changed over time, these three colors were adopted by Mexico following independence from Spain during the country's War of Independence.

The current flag was adopted in 1968, but the overall design has been used since 1821, when the First National Flag was created. The current law of national symbols, Law on the National Arms, Flag, and Anthem, that governs the use of the national flag has been in place since 1984. At that time the Italian tricolor was not in use. The flag now contains the coat of arms, in order to distinguish it from that of Italy. Red, white, and green are the colors of the national liberation army in Mexico.

The central emblem is the Aztec pictogram for Tenochtitlan (now Mexico City), the center of their empire. It recalls the legend that inspired the Aztecs to settle on what was originally a lake-island. The form of the coat of arms was most recently revised in 1968.  Ribbon in the national colors at are the bottom of the coat of arms.

Throughout history, the flag has changed 4 times, as the design of the coat of arms and the length-width ratios of the flag have been modified. However, the coat of arms has had the same features throughout: an eagle, holding a serpent in its talon, is perched on top of a prickly pear cactus; the cactus is situated on a rock that rises above a lake. The coat of arms is derived from an Aztec legend that their gods told them to build a city where they spot an eagle and a serpent, which is now Mexico City. The current national flag, the Fourth National Flag, is also used as the Mexican naval ensign by ships registered in Mexico.

Coat of arms

Coat of arms of Mexico.

The Coat of Arms is charged in the center of the flag, and was inspired by an Aztec legend regarding the founding of Tenochtitlán. According to popular legend, the Aztec people, then a nomadic tribe, were wandering throughout Mexico in search of a sign that would indicate the precise spot upon which they were to build their capital. The war god Huitzilopochtli had commanded them to find an eagle perched atop a prickly pear cactus (nopal in Spanish) growing on a rock submerged in a lake. The eagle would have a serpent trapped in its mouth that it had presently snatched. After two hundred years of wandering, they found the promised sign on a small island in the swampy Lake Texcoco. Here they founded their new capital, Tenochtitlán, which later became known as Mexico City, the current capital of Mexico.

 Meaning of the colors ===

Flag of the Three Guarantees.

The colors of the flag originated from the banner of the Army of the Three Guarantees, which lasted from 1821 until 1823. Originally, the colors had the following meanings:

• Green: Independencia (independence from Spain)
• White: Religión (religion, the Roman Catholic faith)
• Red: Unión (union between the Europeans and Americans)

However, the meaning of the colors changed because of the secularization of the country, which was spearheaded by President Benito Juárez.The new color meanings are as follows:

• Green: Hope
• White: Unity
• Red: Blood of the national heroes

The World Encyclopedia of Flags, a book written by Alfred Znamierowski, also gives the following meaning to the colors of the flag:

• Green: Hope
• White: Purity
• Red: Religion

Since Article 3 of the Flag Law does not give an official symbolism to the colors, other meanings may be given to them. Other groups have used the national colors as part of their own logos or symbols. For example, the Institutional Revolutionary Party (PRI) political party has adopted the national colors as part of their logo. Another political party, the Party of the Democratic Revolution (PRD), also had the national colors as part of their logo, but changed them in the 1990s after a controversy surrounding impartiality issues, while the PRI did not. Several states, such as Querétaro and Hidalgo have incorporated either elements of the national flag, or even the entire flag, into their coat of arms.

History 

Before the adoption of the first national flag, various flags used during the War of Independence from Spain, had a great influence on the design of the first national flag. Although it was never adopted as an official flag, many historians consider the first Mexican flag to be the Standard of the Virgin of Guadalupe, which was carried by Miguel Hidalgo during the Grito de Dolores on September 16, 1810.
 
The Standard became the initial symbol of the rebel army during the Mexican War of Independence. Various other Standards were used during the war. José María Morelos used a flag with and image of the Virgin to which was added a blue and white insignia with a crowned eagle on a cactus over a three-arched bridge and the letters V.V.M. (Viva la Virgen María – "long live the Virgin Mary").The Revolutionary Army also used a flag featuring the colors white, blue and red in vertical stripes. The first use of the actual colors—green, white and red—was in the flag of the unified Army of the Three Guarantees (pictured above) after independence from Spain was won.

While similar to the national flag that is used today, the eagle in these arms is not holding a serpent in his talons and a crown has been affixed to the head of the eagle to signify the Empire. Variants of this flag that appeared in this period also included a naval flag that had the tricolor pattern, but only contained the eagle with the crown above its head. The military also used a similar, square, flag, but the eagle was larger than on the national flag. The national flag was officially decreed by Agustín de Iturbide in November 1821 and first officially used in July 1822. This flag was no longer used upon the abolishment of the empire.

The second national flag that was adopted around the same time as the establishment of the first federal republic in 1823. The new flag chosen for the republic in April of that year, the only difference being the appearance of the central emblem. The crown was removed from the eagle's head and a serpent was placed in the eagle's right talon. Another addition to the flag is a branch of oak and laurel branches, a tradition that was carried over to the current flag. This flag was discontinued in 1864 upon the dissolution of the federal republic.

The third official national flag was that of the Second Mexican Empire. Once again, the national flag used the green, white and red tricolor pattern with the white stripe being charged with the national arms. However, the ratio of the flag was changed from 4:7 to 1:2 and four eagles, which had crowns above their heads, were placed at each corner of the flag. The design, which was ordered by the Emperor Maximilian, gave the arms a look similar to the French Imperial arms, but he decided to add a bit of "Mexican flavor" to the flag. The coat of arms was described in a decree issued in November of 1865 as:

The flag was abandoned in 1867 when Maximilian was overthrown and executed by the Mexican people. The second national flag was adopted once again as the national flag, but it was not officially declared as such.

The current national flag was adopted on September 16, 1968, and was confirmed by law on February 24, 1984. The current version is an adaptation of the design approved by presidential decree in 1916 by Venustiano Carranza, where the eagle was changed from a front-facing to a side-facing position.

Before the adoption of the current national flag, official flags have been used by the government. All of these flags used the tricolor pattern, with the only differences being the changes in the coat of arms, which was still charged in the center of the white stripe. One possible reason for the 1968 flag and arms change was that Mexico City was the host of the 1968 Summer Olympic Games.
 
Around this same time period, the plain tricolor flag that Mexico used as its merchant ensign was also legally abandoned. The reasoning is that without the coat of arms, the flag would not be the Mexican flag; it would have become the Italian flag. There was also debate in 1984 about how the coat of arms will be depicted on the national flag, including the reverse. To solve this problem, a PAN deputy proposed a change to the Law of the National Arms, Flag and Anthem that same year to allow for the eagle to face to the right when the reverse of the flag is displayed. In 1995, the law was changed to include the following:

When the flag is paraded in front of a crowd, those in military uniform must present a salute according to military regulations. Civilians who are present give the following salute to the national flag: standing at attention (firmes), they raise their right arms and place their right hands on their chests, in front of the heart. The hand is flat and the palm of the hand is facing the ground.

Former President Vicente Fox performing the civil salute

This salute is known as the "El saludo civil a la Bandera Nacional" ("The Civil Salute to the National Flag"). When the President is acting in the capacity of the Head of the Armed Forces, he salutes the national flag with a military salute. When the national anthem is played on television to open or close daily programming, the national flag will be shown at the same time.

During certain times of the year, the flag is flown by both civilians and government personnel. Mostly, these events coincide with national holidays and days of significance to the country. During some of these occasions, the flag will be flown at half-mast to honor the death of important Mexicans. These dates are listed in Article 18 of the Law of the National Flag, Arms and Anthem.

The national Día de la Bandera (Flag Day) celebration occurs on February 24. On this day in 1821, all the factions fighting in the War of Independence joined together to form the Army of the Three Guarantees in response to the Plan de Iguala, which was signed by Vicente Guerrero and Agustín de Iturbide, declaring Mexico officially an independent country. General Vicente Guerrero was the first military official who swore allegiance to the national flag. Another flag tradition is that before every Olympics in which Mexico is a participant, the President hands a flag over to the flag bearer, chosen by their peers, to carry with them to the host city.

Pledge of Allegiance

The Pledge of Allegiance to the Flag (Spanish, Juramento a la Bandera literally "Oath to the Flag") is the oath of loyalty to the Mexican flag. It is recited in ceremonies known as Honores a la Bandera (Honors to the Flag) or Asambleas (Assemblies), mainly held in schools or educational centers throughout the country. The protocol indicates that the pledge is recited before the national anthem. The juramento consist of the following: