The murders on the pedestrian street of La Rambla in Barcelona on August 17, 2017 were not the first Islamic terrorist attack in Spain. On March 11, 2004, 192 people were killed, and around two thousand injured, in the Madrid train bombings.
In hindsight, that attack marked a new phase in the modern Islamic Jihad against Europe. After the Madrid bombings, London was hit with deadly bombings on July 7, 2005. In recent years, the frequency of jihadist attacks on European soil has increased dramatically.
It is probably not a coincidence that Spain was an early target of Islamic terror. The Iberian Peninsula, present-day Portugal and Spain, was for centuries under Islamic rule. Militant Muslims have repeatedly made it clear that for them, reconquering Spain is a priority.