[G]enocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:

(a) Killing members of the group;
(b) Causing serious bodily or mental harm to members of the group;
(c) Deliberately infliciting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
(d) Imposing measures intended to prevent births within the group;
(e) Forcibly transferring children of the group to another group.

United Nations Genocide Convention, in force January 12, 1951

The Romans burned Carthage, then sowed the ground with salt.  The biblical Hebrews obeyed the Lord's command to slaughter the inhabitants of Jericho, Ai, Makkedah, Libnah, Hebron, Debir, and many other cities; after sacking Jerusalem in 1099, the Crusaders herded every Jewish man, woman and child into a synagogue, then set it afire.  While the 20th century gave us the weapons and technology needed for efficient mass slaughter, genocide has a long, if not necessarily an honored, history. 

What follows are histories of a few particularly brutal modern genocides.  Some of these mass murders were fueled by ethnic conflicts, others by religious or political motives.  In most cases the perpetrators have escaped punishment … and frequently have gone on to deny that any crime took place at all. 

Armenia
Bangladesh
Cambodia
Germany