Why billions spent on defense haven't shielded Saudi Arabia from Houthi attacks

By Tim Lister, CNN (CNN) - Saudi Arabia spends tens of billions of dollars on defense every year, but is struggling to protect key assets such as airports, refineries and pipelines from missiles and drones fired by Houthi militants from Yemen. Despite acquiring state-of-the-art weapons systems from the United States and Europe and possessing multi-layered