The international Memorial Day held on the 27th of January every year was introduced following the liberation of the concentration camp Auschwitz-Birkenau, the largest Nazi concentration and death camp, by the Red Army.

It is now believed that between 5,000 to 15,000 gay men were sent to concentration camps of whom 3,000 to 10,000 met their deaths as part of the Holocaust.

Source: https://coupleofmen.com/21019-holocaust-remembrance-day-gay-men-pink-triangle/