The following is a timeline of the Yemeni civil war, which began in September 2014.

2014

After several weeks of street protests against the Hadi administration, which made cuts to fuel subsidies that were unpopular with the group, the Houthis fought the Yemen Army forces under the command of General Ali Mohsen al-Ahmar. In a battle that lasted only a few days, Houthi fighters seized control of Sanaa, the Yemeni capital, in September 2014. The Houthis forced Hadi to negotiate an agreement to end the violence, in which the government resigned and the Houthis gained an unprecedented level of influence over state institutions and politics.

2015 In January 2015, unhappy with a proposal to split the country into six federal regions, Houthi fighters seized the presidential compound in Sanaa. The power play prompted the resignation of President Abdrabbuh Mansur Hadi and his ministers. The Houthi political leadership then announced the dissolution of parliament and the formation of a Revolutionary Committee to govern the country on 6 February 2015.

On 21 February, one month after Houthi militants confined Hadi to his residence in Sanaʽa, he slipped out of the capital and traveled to Aden. In a televised address from his hometown, he declared that the Houthi takeover was illegitimate and indicated he remained the constitutional president of Yemen. His predecessor as president, Ali Abdullah Saleh—who had been widely suspected of aiding the Houthis during their takeover of Sanaʽa the previous year—publicly denounced Hadi and called on him to go into exile.

On 19 March 2015, the troops loyal to Hadi clashed with those who refused to recognize his authority in the Battle of Aden Airport. The forces under General Abdul-Hafez al-Saqqaf were defeated, and al-Saqqaf fled toward Sanaʽa. In apparent retaliation for the routing of al-Saqqaf, warplanes reportedly flown by Houthi pilots bombed Hadi's compound in Aden.

After 20 March 2015 Sanaa mosque bombings, in a televised speech, Abdul-Malik al-Houthi, the leader of the Houthis, said his group's decision to mobilize for war was "imperative" under current circumstances and that Al-Qaeda in the Arabian Peninsula and its affiliates—among whom he counts Hadi—would be targeted, as opposed to southern Yemen and its citizens. President Hadi declared Aden to be Yemen's temporary capital while Sanaʽa remained under Houthi control.

Also, the same day as the mosque bombings, al-Qaeda militants captured the provincial capital of Lahij, Al Houta District after killing about 20 soldiers before being driven out several hours later.

Political developments Hadi reiterated in a speech on 21 March 2015 that he was the legitimate president of Yemen and declared, "We will restore security to the country and hoist the flag of Yemen in Sanaʽa, instead of the Iranian flag." He also declared Aden to be Yemen's "economic and temporary capital" due to the Houthi occupation of Sanaʽa, which he pledged would be retaken.

In Sanaa, the Houthi Revolutionary Committee appointed Major General Hussein Khairan as Yemen's new Defence Minister and placed him in overall command of the military offensive.

Control of Taiz

On 22 March 2015, Houthi forces backed by troops loyal to Saleh entered Taiz, Yemen's third-largest city, and quickly took over its key points. They encountered little resistance, although one protester was shot dead and five were injured. Western media outlets began to suggest Yemen was sliding into civil war as the Houthis from the north confronted holdouts in the south.

On 14 December 2015, the pro-Saleh Yemeni Army and Houthi militants carried out a strike with an Tochka ballistic missile against a military camp that was being used by troops of the Saudi-led coalition, south-west of the city of Taiz.

Western Yemen advance

On 23 March 2015, Houthi forces advanced towards the strategic Bab-el-Mandeb strait, a vital corridor through which much of the world's maritime trade passes. The next day, fighters from the group reportedly entered the port of Mocha.

On 31 March 2015, Houthi fighters entered a coastal military base on the strait after the 17th Armoured Division of the Yemen Army opened the gates and turned over weapons to them.

On 2 April 2015, Mahamoud Ali Youssouf, the foreign minister of Djibouti, said the Houthis placed heavy weapons and fast attack boats on Perim and a smaller island in the Bab-el-Mandeb strait. He warned that the weapons posed "a big danger" to his country, commercial shipping traffic, and military vessels.

Southern offensive

Battle of Dhale

On 24 March 2015, Houthi forces seized administrative buildings in Dhale (or Dali) amid heavy fighting, bringing them closer to Aden. However, Houthi fighters were swiftly dislodged from Ad Dali' and Kirsh by Hadi-loyal forces.

Fighting over Dhale continued even as the Houthis advanced further south and east. On 31 March 2015, Hadi loyalists clashed with the Houthis and army units loyal to Saleh.

On 1 April 2015, a pro-Houthi army brigade was said to have "disintegrated" after being pummeled by coalition warplanes in Ad Dali. The commander of the 33rd Brigade reportedly fled, and groups of pro-Houthi troops withdrew to the north. The city reportedly fell into pro-government hands by the end of May.

Fighting in Lahij On 24 March 2015, in the Lahij Governorate, heavy fighting erupted between Houthis and pro-Hadi fighters. The next day, Al Anad Air Base, 60 kilometers from Aden, was captured by the Houthis and their allies. The base had recently been abandoned by United States of America USSOCOM troops. Defense Minister Mahmoud al-Subaihi, one of Hadi's top lieutenants, was captured by the Houthis in Al Houta and transferred to Sanaʽa. Houthi fighters also advanced to Dar Saad, a small town, 20 km north of Aden.

On 26 March 2015, after clashes erupted in Aden, Hadi loyalists counterattacked as a Saudi-led military intervention got underway. Artillery shelled Al Anad Air Base, forcing some of its Houthi occupants to flee the area. Saudi airstrikes also hit Al Anad. Despite the airstrikes, the southern offensive continued.

Fighting reaches Aden

In Aden, military officials said militias and military units loyal to Hadi had "fragmented" by 25 March, speeding the Houthi advance. They said the Houthis were fighting Hadi's troops on five different fronts. Aden International Airport suspended all flights. Fighting reached Aden's outskirts on 25 March 2015, with pro-Saleh soldiers taking over Aden International Airport and clashes erupting at an army base. Hadi reportedly fled his "temporary capital" by boat as the unrest worsened. On 26 March 2015, he resurfaced in the Saudi capital, Riyadh, where he arrived by plane and was met by Saudi Prince Mohammad bin Salman Al Saud.

Over the following days, Houthi and allied army forces encircled Aden and hemmed in Hadi's holdouts, although they encountered fierce resistance from the embattled president's loyalists and armed city residents. They began pressing into the city center on 29 March 2015 despite coalition air strikes and shelling from Egyptian Navy warships offshore.

On 2 April 2015, the compound that has been used as a temporary presidential palace was taken by the Houthis, and fighting moved into the central Crater and Al Mualla districts.

A small contingent of foreign troops was reportedly deployed in Aden by early May, fighting alongside anti-Houthi militiamen in the city. Saudi Arabia denied the presence of ground troops, while Hadi's government claimed the troops were Yemeni special forces who had received training in the Persian Gulf and were redeployed to fight in Aden.

On 21 July 2015, forces loyal to Hadi recaptured Aden with support from Saudi Arabia in Operation Golden Arrow after months of fighting. This allowed supplies to finally reach the port city giving civilians desperately needed aid.

On 22 July 2015, a Saudi military plane landed in Aden international airport filled with relief aid. Also, a UN ship docked in Aden carrying much-needed relief supplies, the first UN vessel to reach the city in four months. Another ship sent by the UAE also delivered medical aid. On 21 July 2015, a UAE technical team had arrived to repair the tower and passenger terminal at Aden international airport, heavily damaged in clashes. On 24 July 2015, a military plane from the UAE arrived filled with relief aid.

On 4 August 2015, Houthi forces were pushed back from the Al-Anad airbase, by Pro-Hadi forces.

On 17 October 2015, Saudi Arabia confirmed the arrival of Sudanese troops into Aden for the purpose of bolstering the Saudi-led coalition.

Other campaigns

Abyan Governorate

The Houthis racked up a series of victories in the Abyan Governorate east of Aden in the days following their entrance into Hadi's provisional capital, taking control of Shuqrah and Zinjibar on the coast and winning the allegiance of a local army brigade, but they also encountered resistance from both pro-Hadi army brigadiers and al Qaeda in the Arabian Peninsula militants. Zinjibar and Jaar were recaptured by AQAP on 2 December 2015.

Hadhramaut Governorate

Al-Qaeda in the Arabian Peninsula took control of Mukalla in the eastern Hadhramaut Governorate on 2 April 2015, driving out soldiers defending the city with mortar fire and springing some 300 inmates from prison, including a local al-Qaeda leader.

Local tribal fighters aligned with Hadi surrounded and entered Mukalla on 4 April 2015, retaking parts of the city and clashing with both al-Qaeda militants and army troops. Still, the militants remained in control of about half of the town. In addition, al-Qaeda fighters captured a border post with Saudi Arabia in an attack that killed two soldiers.

On 13 April 2015, Southern militia said they took control of the army base loyal to the Houthis near Balhaf. Mukalla city was recaptured in late April 2016, after UAE and Hadi loyalists troops entered the city, killing some 800 AQAP fighters.

On 12 June 2015, Al-Qaeda in the Arabian Peninsula leader Nasir al-Wuhayshi was killed in a US drone strike in Mukalla.

Lahij Governorate

Although the Houthis took control of Lahij on the road to Aden, resistance continued in the Lahij Governorate. Ambushes and bombings struck Houthi supply lines to the Aden front, with a land mine killing a reported 25 Houthi fighters on their way to Aden on 28 March 2015.

Shabwah Governorate

Fighting also centered on the Shabwa Province, in the oil-rich Usaylan region, where Al-Qaeda in the Arabian Peninsula (AQAP) and Ansar al-Sharia hold sway. On 29 March 2015, 38 were killed in fighting between the Houthis and Sunni tribesmen. Tribal sources confirmed the death toll, and claimed only 8 of them were from their side, with the other 30 either Houthis or their allies from the Yemeni military.

On 9 April 2015, the Houthis and their allies seized the provincial capital of Ataq. The takeover was facilitated by local tribal chiefs and security officials. AQAP seized Azzan, and Habban in early February 2016.

Elsewhere On 22 March 2015, in the province of Marib, 6 members of pro-Hadi tribes were killed during fighting against Houthis.

On 23 March 2015, 15 Houthis and 5 tribesmen were killed in clashes in the Al Bayda Governorate. During the fight between Hadi loyalists and Houthi militiamen in Sanaa, the Ethiopian embassy was reportedly struck by shelling on 3 April 2015. The Ethiopian government said the attack appeared to be unintentional. No injuries at the embassy were reported.

On 7 April 2015, armed tribesmen drove off Houthis who had set up a makeshift camp in southern Ibb Governorate and seized their weapons.

Between 17 and 18 April 2015, at least 30 people were killed when the Houthis and allied army units attacked a pro-Hadi military base in Taiz. The dead included 8–16 pro-Hadi and 14–19 Houthi fighters, as well as 3 civilians. Another report put the number of dead at 85.