The image would look right at home on Instagram: a group of seemingly carefree young men in uniform flirting with two fashionable women on a sunny summer day on New York’s Brighton Beach. But the photograph was taken more than a century ago, during World War I: a moment of joy in a period now remembered for relentless tragedy. “These photographs turn what we think we know on its head and open our eyes to the humanity in a time that was inhumane and catastrophic,” says Lora Vogt, a curator…