On Tuesday, Russian Defense Minister Sergei Shoigu announced that Moscow had finalized the delivery of 49 units of S-300 air defense systems to Syria. The decision to boost the security of Russian troops on the ground follows an accidental downing of an Il-20 aircraft on September 20. The Russian Defense Ministry has released a video of S-300 air defense systems being unloaded in Syria from an An-124 Ruslan transport aircraft. The video was aired by Russian TV channel Zvezda. Sergei Shoigu has said that the Syrian army will spend the next three months learning how to use the complexes. The defense minister has said that Moscow will take a number of measures to boost the safety of its troops in Syria, including the deliveries of the S-300 systems. This comes in the wake of the crash of an Il-20 military plane off the coast of Syria, which Russia believes Israel was responsible for. The Russian military has blamed the crash on the Israeli Air Force, noting that an Israeli plane had used the Russian plane as a shield against Syrian air defense systems. Israel has refuted the accusations and stressed that Tel Aviv had warned Moscow about the air raid in the region in a timely fashion.