Iran is home to one of the Middle East's largest militaries, but not necessarily the region's best. That Iran is even capable of threatening regional rivals, at least with the technology it has, is actually somewhat of a surprise: Decades of sanctions have prevented Tehran from effectively upgrading its arms and military equipment, leaving it far behind countries it would consider its rivals. Now that the sanctions have been lifted , Iran is trying to catch up to those rivals, including Saudi Arabia , Turkey and the United Arab Emirates, which have spent hundreds of billions of dollars on some of the most advanced weaponry on the international market. Decades of sanctions have also made it difficult for Iran to source spare parts to repair and maintain its existing military equipment, particularly Western weaponry acquired when Shah Mohammad Reza Pahlavi was in power.