It wasn't CIA drones, NSA wiretapping, or the constellation of US early warning satellites that first warned the US that a Scud missile had been fired at Saudi Arabia by Houthi Yemeni rebels, it was a hashtag on Twitter: "#scudlaunch".

“The first warning of that event: ‘hashtag scudlaunch,’” Marine Lt. Gen. Vincent Stewart, the head of the Pentagon’s Defense Intelligence Agency (DIA), told a meeting of intelligence contractors Thursday night. The Houthi rebels themselves released the video on Twitter. Royal Saudi forces later said in a statement that they had shot down the Scud.

Twitter, YouTube videos, and other social media released by fighters online have become increasingly important in information gathering. In 2013, using this “open-source information” British blogger Eliot Higgins, helped finger the Syrian government using chemical weapons against its own people.

In 2014, Higgins and a group of citizen journalists, helped identify the missile launcher that shot down Malaysia Airlines Flight 17 over Ukraine as belonging to pro-Russian separatists, a conclusion later supported by American and German intelligence services.

Facts about: yemen and missiles

 The Scud is a Soviet road-mobile ballistic missile developed in 1957. It's been used by states including Iraq, North Korea and Syria and is responsible for hundreds of deaths. The Scud can carry a conventional high explosive warhead, a nerve gas warhead, or a nuclear warhead up to 430 miles.  

 Yemen is currently locked in fighting between the loyalist forces of President Mansour Hadi backed by Saudi Arabia and other Arab states and the Houthi rebels and their allies supporting the ousted former president Ali Abdullah Saleh, backed by Iran. The minority Shia Muslim Houthis are fighting over perceived Sunni Muslim government oppression. Yemen is located on the strategically important Bab-el-Mandeb strait on the Arabian Peninsula. Whoever controls access to the strait controls access to the majority of the world’s oil.

 Cover: Wikipedia