US Civil War:  Democrats fought to keep their slaves.
1 million casualties.
Democrat James K Polk, Mexican-American War.
17,000 casualties.
WWI--Democrat Woodrow Wilson and a Democrat Congress authorized the carrying of war materiel on US merchant ships, thus making those ships legitimate military targets.
320,000 casualties.
WWII--Democrat FDR and a Democrat Congress authorized the carrying of war materiel on US merchant ships, and naval vessels to protect such ships and fire on German commerce raiders, thus initiating violence against a foreign power.  
1,076,000 casualties.
Korea--Democrat Harry Truman and a Democrat Congress authorized US involvement in a land war in Asia.
128,000 casualties.
Vietnam--Democrat Harry Truman authorized economic aid for another land war in Asia. Democrat JFK sent the first combat troops. Lyndon BJ sent thousands more US combat troops, all under Democrat Congresses.
211,000 casualties.
Dominican Republic--Democrat Lyndon BJ
330 casualties.
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75% of violent criminals identify as Democrats.
The solution is obvious.
Outlaw the Democratic Party under RICO, arrest and jail all members, and US violence will largely disappear.