bloodletting

Short definition from Wiktionary

Noun

1. 1
   The archaic practice of treating illness by removing some blood, believed to be tainted, from the stricken person.
2. 2
   The diminishment of any resource with the hope that this will lead to a positive effect.
3. 3
   A circumstance, such as a battle, where a large amount of blood is likely to be spilled through violence.

Verb

1. 1
   present participle and gerund of bloodlet