In March 2015, Saudi Arabia led a coalition of 10 Arab countries, dispatching more than 100 warplanes and 150,000 troops to intervene in the Yemeni civil war, with the goal of eliminating the Houthi rebels. Yemen, located in the southwestern part of the Arabian Peninsula, has had little presence, but has been in the international news in recent decades, in large part because of the Houthis. This name sounds like a guerrilla, nicknamed the "Slipper Army" by netizens, but now it has advanced equipment such as ballistic missiles and drones, and has a certain ability to fight in the air and at sea. 
The Houthis take their name from their founder, Hussein Houthis. He was born in the 50s to a large family in the northern province of Saada in northern Yemen, and his father was a well-known scholar of the Zayd sect, a branch of Shiism. Naturally, the Houthis followed the path of teachers. Here is a brief history of Yemen to help you understand the Houthis. Yemen has a history of more than 3,000 years, known as the Kingdom of Sheba in ancient times, was conquered by the Arab Empire in the 7th century AD, and was incorporated into the territory of the Ottoman Empire in the 16th century. Most of the Zaideites live in the mountainous areas of the northern province of Saada, where the terrain is difficult to defend and difficult to attack, but due to the influence of the Red Sea monsoon, the land is not barren and self-sufficient, and gradually forms a system of Imam rule. The Zaide faction is a fierce people, although conservative but does not reject foreign technology, and is good at absorbing and creating, and the main body of the Houthis is the Zaide faction. Therefore, it is not surprising that they, with the help of external forces, build up their own missile and drone units, and even by dismantling captured enemy equipment, DIY air defense systems shoot down Saudi fighters. 
In the 19th century, the British invaded Yemen and occupied the port of Aden. The Ottoman Empire was too busy with the Russo-Turkish war to take care of it, and the British gradually occupied southern Yemen and established colonies. At the end of World War I, in 1918, when the Ottoman Empire was about to collapse, the Zaide priests broke away from the Ottomans and established the Imam Kingdom, with the capital of Sana'a and control of North Yemen. South Yemen is still occupied by the British. In 1962, under the influence of Nasser in Egypt, a group of young military officers in North Yemen overthrew the Imam Kingdom and established the Yemeni Arab Republic, which was relatively pro-Western in terms of diplomacy. During this period, South Yemeni nationalists formed the Left National Front to rebel against British colonization with the support of the Soviet Union. In those years, Britain spent half of its annual military expenditure in Yemen, and finally it couldn't stand it anymore and withdrew in 1967. South Yemen established a pro-Soviet republic with its capital in Aden. Compared with East and West Germany and North and South Vietnam, North and South Yemen are relatively friendly, although there have been several conflicts, but the scale is very small, the duration is also very short, and the two sides have a strong desire to merge and reunify. The overthrown Zade clergy class was left out in the cold in the mountains of Saada province and could not intervene in the affairs of the state. In the 80s, the economy of North Yemen developed to a certain extent, but the province of Saada was far below average. Some clergy could not stand the poverty, so they compromised with the secular authorities and went to the city to live comfortably. 
Against this backdrop, Hussein Hussein, who grew up to take over the mantle of his father, was determined to revive the Zaide sect and create a youth faith organization to spread conservative ideas among young people. In 1990, the stormy Soviet Union could no longer afford to aid South Yemen, and South Yemen had a financial crisis and could not play any longer, so it took the initiative to propose a merger to the North. In May of the same year, North and South Yemen were reunified. The decline of the Soviet Union put South Yemen at a disadvantage, accepting the former North Yemen**, the strongman Saleh, who had been in power for 12 years, as the reunification**, the former supreme leader of South Yemen as the deputy**, and the North accounted for more than half of the parliamentary seats. However, the armies of North and South Yemen have not been united, and the traditional forces in the region are deeply entrenched, and most of the larger tribes have their own armed forces, and there is a dark current behind the apparently unified Yemen. Saleh, a soldier, maneuvered between various forces, maintaining a delicate balance, and was known as the "dancing bull man on the head of a snake". After reunification, Yemeni Sunnis accounted for 69%. Saleh, who belonged to the Zaide faction, needed to win over Hussein Houthi, who already had some influence, for balancing the balance. With the support of the authorities, the "Youth Faith" has grown rapidly. As a result, the Houthis were elected to parliament in 1993, the same year that the former South Yemen region discovered large oil fields, and the distribution of oil profits ignited the conflict between the North and the South. The following year, when the former South Yemeni military declared independence, Saleh immediately sent troops to conscript, and the northern army was already superior in strength, and it took only two months to put down the rebellion. In the process, Saleh found that the Wahhabi militants, who had been expelled by Egypt and had nowhere to go but to Yemen, were very effective in fighting the separatists in the south, so he turned a blind eye and acquiesced in their activities in Yemen. These men later became the base offshoot. Wahhabi is a Sunni offshoot, and the Houthis, as the leader of the Shiite branch of Zaid, are extremely dissatisfied with Saleh's approach, and the two sides are drifting apart. 
In the late '90s, the Houthis stepped down from parliament and traveled around the Middle East, feeling that the Iranian model best suited the Zaidist ideals. During this time, he is said to have established contacts with Khamenei and Allah leader Nasrallah. After returning home in 2000, the Houthis became radical, advocating the creation of a theocratic Yemen to counter the infiltration of Saudi Arabia, a Sunni-led brother. His ideas were supported by the tribes of Saada province, the traditional territory of the Zade, and under his leadership, tens of thousands of members of the youth faith also rose to the occasion and began to form an armed force. In March 2003, when the US-British coalition invaded Iraq, Saleh, who had been in office for more than 20 years, supported the United States for various purposes. Houthis and supporters have flaunted the banner of "anti-American and anti-Israel", accusing Saleh of betraying Yemeni interests to please the United States and Saudi Arabia. Saleh believes that these people shout to bring down the United States today, and they may have to shout to bring down themselves tomorrow. Ordered the arrest of the **, and arrested more than 1,000 young members of the faith, and the contradictions between the two sides intensified. In June 2004, Saleh wanted to de-escalate the situation and invited the Houthis for an interview, which he refused. Dismissed, he ordered the arrest of Houthis. The Houthis led members of the "Youth Faith" to rebel in Saada province. Saleh accused the Houthis of being funded by Iran and trying to stir up trouble in Yemen and sending troops to suppress them. The province of Saada borders Saudi Arabia, which fears that the Shiite Houthi assembly will endanger itself and has also helped the Yemeni authorities to quell the insurgency. After the Houthis were killed in a battle in September, his younger brother, Abdul Houthi, who was more than 20 years younger, took up the mantle and changed the name of the youth faith to the Houthis as a sign of eternal followership. 
Born in 1982, Hobdul is young but calm, leading the Houthis to withstand the joint attack of the ** army and Saudi Arabia. This is mainly due to the mountainous nature of Saada Province, where the Houthi main body Zayd is inhabited, familiar with the terrain, the people are fierce, and with the support of Iran and the blessing of the teachings, they have a strong will to fight. Although Saudi Arabia, which has the largest military expenditure in the Middle East every year, is well-equipped, the military literacy of the users is difficult to describe, and it has not bargained much. In 2011, the Arab Spring swept the Middle East, and Saleh, who had been the best for decades, could no longer play the balancing act, and was forced to resign, and Deputy Hadi took over. But the situation remains chaotic and the forces are ready to move. The Houthis seized the opportunity to establish themselves in Saada province, independent of the Yemeni authorities, and successively annexed two neighboring provinces to open up access to the Red Sea. The assistance received by the secondary sponsor is also conducive to entering the capital Sana'a at any time. During this period, Abdul built a powerful propaganda machine, including a television station and 25 publications, and his influence was further expanded. In August 2014, the Houthis instigated Sana'a supporters to go to war on the pretext of repression, taking control of the capital Sana'a in just one month, placing Hadi under house arrest and forcing him to resign. Subsequently, the provisional ** was formed and marched to the south, and the civil war in Yemen broke out. 
The Houthis quickly took control of 18 Shia-majority provinces in northern and central Yemen, seizing large quantities of military supplies. However, in the ensuing advance, the Houthis were blocked by Sunni tribal forces and al-Qaeda branches. At the end of February 2015, Hadi managed to escape from house arrest and went to Aden, the former capital of South Yemen, to announce that he had withdrawn his resignation. The Gulf Cooperation Council (GCC), led by Saudi Arabia, has moved their embassies to Aden to show their support. At Hadi's request, Saudi Arabia organized a coalition of ten Arab countries, of which Saudi troops accounted for the vast majority. With U.S. intelligence support, the Arab coalition intervened in Yemen's civil war with the intention of eliminating the Houthis, which were also a threat to themselves, and restoring their legitimate authority to international recognition. However, these actions did not help, and the war shows no end to this day. In addition to the Houthi Yemeni army, there are also the former South Yemen separatist forces, the forces that support the former Saleh and the al-Qaeda branches and local tribal forces, which are mixed with sectarian contradictions and conflicting interests. In short, just one word. "Chaos". 
The Houthis, once the "slipper army", have become stronger and stronger in the process, and now they are similar to the regular army, with many advanced equipment, and have attacked the parades of Saudi and Yemeni authorities with drones and missiles, which can be said to be quite arrogant. Under this scenario, if the situation in the Middle East changes abruptly, the Houthis may be able to unify Yemen.