Yemen is being torn apart by a toxic political crisis between a weak national government and a rebel movement known as the Houthis, who have taken over the capital of Sanaa and ousted the president. The resulting power vacuum has allowed extremists groups like Al Qaeda in the Arabian Peninsula and ISIS to expand their influence in the country.

Amid the escalating turmoil, a coalition of nations led by Saudi Arabia has launched a military campaign against the Houthi rebels, raising the odds that the fight for Yemen could soon spillover into a much larger regional and sectarian war.

So who is fighting who in Yemen, and what does each side in the increasingly complex battle stand for?