Yemen is a country composed of different tribal realities, reunited during the twentieth century in two different states from the political and religious point of view, but culturally similar: in the most fertile and populous North prevails the Zaidite sect of Shiism, which had historically ruled the area; while the South has always been predominantly Sunni. The different denominations coexisted without distinction.
The unity of the country dates back to 1990, followed in 1994 by a brief conflict between the supporters of the two former governments.
President Ali Abdallah Saleh, former president of the majority North, chooses to govern leaning on the new al-Islah [Reform] party, ideologically close to the Muslim Brotherhood. They promote a rigid and divisive vision of Islam that provokes a religious, political and finally military awakening of the tribes of the North, predominantly Zaidites.
Since 2011, after the deposition of the president, the different political realities of the country clash for power, in a very fragmented reality, often made of very fluid tribal alliances, and influenced by regional politics and by the presence of terrorist groups: the Ansar Allah movement, founded and led by the zaidite Huthi family, seems to prevail at first, occupying almost all the North with the capital Sana'a, and reaching the southern port of Aden (former capital of South Yemen and new provisional capital).
This leads to a military reaction of Saudi Arabia fearful of a Shiite-led state on its borders, in support of the legitimate Yemeni government led by President Abd Rabbo; the tribes of the South instead have the support of the United Arab Emirates and oscillate between requests for autonomy or full independence, often fighting with the international coalition but also episodically against the government (e.g. for the control of Aden).
The Saudi-led coalition sees the military logistical support of many countries, including Western ones (including the USA); despite the massive economic investment, it has not yet achieved any decisive success, and the most significant part of the country is still controlled by the government supported by Ansar Allah, internationally supported by Iran; the many agreements between the three factions in conflict (Ansar Allah, loyalists and separatists of the South) have never produced lasting effects, while the humanitarian situation has long been in collapse.
