The phrase "white handkerchiefs" refers to a symbol of surrender or truce. It means someone is waving and showing a white cloth, typically a handkerchief, to indicate that they want to stop fighting or peacefully resolve a conflict. Full definition
WALL Painted in Porcelain Doll and White Handkerchief matt emulsions, as before. (livingetc.com)
They live in perpetual fear of the time they call The Coming Of The Great White Handkerchief. (religion.blogs.cnn.com)
The atmosphere was toxic and some Villa fans were seen waving white handkerchiefs, months after those on the pitch had surrendered to relegation. (avillafan.com)