Read our Privacy noticeFears have mounted over the world’s two major wars converging after Ukraine attacked an Iranian vessel in the Caspian Sea, with Tehran vowing to respond. Why is the Caspian Sea important? The Caspian Sea is bordered by five countries, including Iran and Russia. How could Iran attack Ukraine? “My guess is that the Iranians will shrug off what happened in the Caspian Sea as the cost of doing business.”