Many of the principle weapons that the Nazis used during World War II had their first trial in combat in Spain - the Messerschmitt 109 fighter plane for example, the Stuka dive bomber, the 88 millimeter artillery piece, which could be used both for antiaircraft purposes and also shelling on the ground. And American soldiers were the victims of these things in Spain, American volunteers. So this war was really a testing ground for Hitler. And he learned a great deal from it about the strengths and weaknesses of these different weapons.

I think writers can respond by writing about the refugee crisis, by looking at problems faced by migrants, by trying hard to portray them as the human beings that they are.

Many of the principle weapons that the Nazis used during World War II had their first trial in combat in Spain - the Messerschmitt 109 fighter plane for example, the Stuka dive bomber, the 88 millimeter artillery piece, which could be used both for antiaircraft purposes and also shelling on the ground. And American soldiers were the victims of these things in Spain, American volunteers. So this war was really a testing ground for Hitler. And he learned a great deal from it about the strengths and weaknesses of these different weapons.

In his fierce, bold determination to see the lives of modern-day slaves up close, Benjamin Skinner reminds me of the British abolitionist of two hundred years ago, Zachary Macaulay, who once traveled on a slave ship across the Atlantic, taking notes. Skinner goes everywhere, from border crossings to brothels to bargaining sessions with dealers in human beings, to bring us this vivid, searing account of the wide network of human trafficking and servitude which spans today's globe.

Ronald Reagan perfected the subtler version long ago by talking about "welfare mothers" - a code phrase for people of colour.

I think one thing writers can do is point out that you don't have to say openly racist things, like [Donald] Trump, to be a racist or a xenophobe.

I think in many ways, the Spanish Civil War was the first battle of World War II. After all, where else in the world at this point did you have Americans in uniform who were being bombed by Nazi planes four years before the U.S. entered World War II? Hitler and Mussolini jumped in on the side of Francisco Franco and his Spanish nationalists, sent them vast amounts of military aid, airplanes, tanks - and Mussolini sent 80,000 ground troops as well - because they wanted a sympathetic ally in power. So I think it really was the opening act of World War II.