The United Nations has estimated that about 150,000 people have been displaced by instability in Saada province since sporadic fighting broke out in 2004.
The Saada province rebellion began in June 2004 when Husain al-Houthi founded an organisation called Shabab al-Mumineen, the Believing Youth movement, and announced an uprising against the Yemeni government.
The imam said his vision was to establish Zaydi sharia law to defend his community against discrimination, rather than the constitution brought by the republicans once the Zaydi Imamate was defeated.
Yahya al-Houthi continued the insurgency soon after his brother Husain's death in June 2005.
The movement has at times offered to end its struggle, in a region where access to health, education and electricity is extremely limited.
In a letter sent to Sanaa in 2006 it asked emissaries be sent to discuss terms. "But if injustice continues with killing, destroying, and imprisonment... then the trouble will not be solved, but will become more complicated and the gap will become even wider," the message warned.
No negotiations have ever taken place, and the capital has continued to attack the rebel movement every summer since 2007.