With Corbynism has come the return of big ideas and big politics on the left. The Labour party is now seen as being at the forefront of contemporary left politics, bucking the downward trend of its sister parties. In this article, originally published by Renewal, Adam Klug and Emma Rees argue that a renewed internationalism based on cooperation across borders between parties of the left can help bring new ideas, new techniques, new solidarities and a new sense of optimism when times are tough.