Russian aircraft on Wednesday took off from Iran for the second time to conduct airstrikes in Syria. A member of Iran’s parliament said Wednesday that Russian aircraft used the Shahid Nojeh Air Base near Hamedan to refuel before striking targets in Syria, according to the Associated Press. Russia’s announcement that it used the Iranian base for strikes marks the first time it has stationed a significant number of troops in the country since World War II, according to the AP. The Russian Ministry of Defense said the second round of strikes hit two command posts and two training camps. The State Department, in a Tuesday briefing, said Russia’s use of the Iranian base is “unfortunate but not surprising or unexpected.” Russia is still targeting moderate Syrian opposition forces, which “only makes more difficult what is already a very contentious and complex and difficult situation,” State Department spokesman Mark Toner said. The State Department is investigating whether the Russian use of the base violates UN Security Resolution 2231, prohibiting the supply, sale, and transfer of combat aircraft to Iran. A spokesman for Russia’s Ministry of Defense said in a Wednesday statement the resolution only covers use of aircraft in Iran, according to NBC News.