If the first wars were fought with sticks and stones, modern warfare is a high-tech battlefield where social media has emerged as a surprising — and effective — weapon. From Russian hacking to influence the American election to online recruitment for terror groups such as ISIS, an array of players are using false news and bogus accounts to stoke fear, incite violence and manipulate outcomes. Authors Peter W. Singer and Emerson T. Brooking describe this as “likewar,” a term that plays on the Facebook “like” feature. In their new book, LikeWar: The Weaponization of Social Media , they explain how these platforms have become persuasive tools of propaganda. The recently joined the Knowledge at Wharton radio show on Sirius XM to discuss their work. An edited transcript of the conversation follows. Knowledge at Wharton: It is incredible how social media has developed and expanded rapidly in the last 20 years, and the impact it has had on politics. Peter Singer: It’s absolutely fascinating.…