Do all American voters need to understand this? The Syrian war is extraordinarily complicated, and even the experts have to work hard to keep up with all the details. Well, what everyone should understand is that Syria is a humanitarian catastrophe of historic proportions, with consequences reaching across the globe. It would help if voters knew that a brutal dictator, Bashar al-Assad, is using poison gas and dropping barrel bombs on civilians; that Russia's Vladimir Putin is backing him, and that the rebels fighting the government include both radical Islamists and moderate Kurdish forces fighting alongside groups of moderate Arabs.