<unk>  have been used in military dating back to the Roman army although the term was not coined until 1718.
In the US military,<unk>  were issued to soldiers from the time of the American Civil War up till World War I. However,<unk>  fell out of favor during World War II.
During WWI four recommendations regarding the use of<unk>  were given. 1) Never cover a<unk> 2) Write that a<unk> was applied on the medical tag 3) If conscious tell the service member to verbally inform medical providers that a<unk> was applied 4) Leave a<unk> in place for up to 6 hours only
During the Vietnam conflict, 2500 US casualties were noted to have perished because of hemorrhaging from an extremity wound alone that is no other significant injuries were noted on the casualty.
Based on experience from use over the last decade,<unk>  have been shown to be safe and life-saving. The reason<unk>  fell out of favor with the US military was due to poor patient transport out of no man's land in WWI which lead to ischemic complications.
Extremity hemorrhage is the most frequent cause of preventable battlefield deaths thus early control of severe hemorrhage is critical.<unk>  are a proven effective means of controlling extremity hemorrhage 
Damage to extremity is rare if<unk> is left on for < 2 hours (recall that TQ are frequently used in surgeries which last several hours). This risk of damage to the limb is considered acceptably small rather than having the casualty expire due to exsanguination.
Tourniquet 
Hair tourniquet
Enoxaparin
Unfractionated heparin
Thrombolytics
IVC filter
Vasopressors
Digital block