The Iran-backed Houthi rebels' strikes and guerrilla tactics have made it difficult for Saudi forces to gain the upper hand in the Yemeni civil war. Saudi Arabia's energy minister has vowed to respond to the attacks on the kingdom's airports and oil and gas facilities by Yemen's Iran-backed Houthi movement. The Houthis said they launched the attacks in retaliation for "brutal Saudi aggression" against areas they control in western Yemen. Tap the link in @BBCNews's bio to follow this story. #Houthis #Yemen #BBCNews