alliance with supporters of former President Saleh, said Al Rowas. This facilitated the Houthissouthward expansion, but the alliance is fragile, she said, not least because Saleh in the past waged military campaigns against the Houthis. Al Qaeda's Yemen affiliate AQAP is perhaps the best-known group internationally. It first emerged in Saudi Arabia in 2002, but thanks to the efforts of Saudi authorities was a mostly a spent force by 2005, according to analysis from Jane's World Insurgency and Terrorism. It re-emerged, reinvigorated, in Yemen in 2009 after the Saudi outfit merged with a Yemeni al Qaeda counterpart. Besides battling the Yemeni government and Houthis, it has been involved in international terror attacks, including the failed 2009 attempt to bring down an airliner over Detroit. The Muslim Brotherhood is also a powerful group in Yemen -- in the shape of the Al Islah Party -- and is well represented in the transitional government. It loathes the Houthis and has its own militias. The fighting in Yemen also provides an opening to ISIS, which is keen to outflank al Qaeda and prove itself the true defender of the faith. In November, ISIS leader Abu Bakr al-Baghdadi called on Yemeni Sunnis to resist the Houthis. There are also a number of heavily armed rural tribes that will fight for control over their territories. While in power, Hadi and the government of Prime