Moscow officials denied the Red Cross' request to investigate, but evidence pointed to a spring 1940 date.  
The story was broken by Berlin Radio in 1943, and within a week the expatriate Polish government under Premier Sikorski had filed an official complaint with the International Red Cross.  Moscow officials denied the Red Cross' request to investigate, but evidence pointed to a spring 1940 date.  The perpetrators were probably the Russian NKVD, and over 2,000 Polish officers were found shot in the head.  FTP, identify the massacre named after a forest near Smolensk (SMALL-ensk), Russia.
The story was broken by Berlin Radio in 1943, and within a week the expatriate Polish government under Premier Sikorski had filed an official complaint with the International Red Cross.  
Katyn Forest Massacre (CAT-ain but accept anything phonetic)