The soldiers' bestiality during the war was shocking.

bestiality 是由形容词 bestial（野兽般的、残忍的）加上名词后缀 -ity 构成的名词。bestial 来自拉丁语 bestia（野兽），bestiality 字面意思是"兽性"，引申为"残暴、野蛮的行为"。