Saudi Arabia claimed the barrier was necessary to protect from terrorism and smuggling weapons and illegal drugs — namely qat ( and Yemen ’s most important export , with border tribes reportedly earning upwards of £ 100 million a year ) . Specifically , Saudi Arabia claimed that smugglers provide weapons to radical Islamists within Saudi Arabia and were the source of explosives used in attacks like the 2003 Riyadh compound bombings , which killed 35 and injured over a hundred . Two years after the Yemeni Revolution of 2011 , the country found itself a " haven for foreign terror fighters " where the Yemen-based Al-Qaeda in the Arabian Peninsula has " remained resilient and even enjoyed a resurgence "
Riyadh compound bombings
Riyadh compound bombings
Saudi–Yemen barrier