To cite a few statistics:

From the Revolutionary War to the Gulf War, American casualties only:

Military service during war        42,348,460
Battle deaths        651,008
Other deaths in service (theater)        13,998
Other deaths in service (nontheater)        525,256
Nonmortal woundings        1,431,290
Living war veterans        17,578,5003
Living veterans        25,038,459

From July 1 to November, 1916, the Battle of the Somme:

By the end of the battle, the British Army had suffered 420,000 casualties including nearly 60,000 on the first day alone. The French lost 200,000 men and the Germans nearly 500,000.

The Battle of Lesnaya, 1708:

The Swedes lost 6,307 men in the battle, more than half of them prisoners. The rest of the force finally joined Charles on October 8, but served only to increase his problem of feeding the army. Russian casualties totaled 1,111 killed and 2,856 wounded, about one-third of those engaged.

Korea, 1950-1953:

The Korean War finally ended in July 1953. Left in its wake were four million military and civilian casualties, including 33,600 American, 16,000 UN allied, 415,000 South Korean, and 520,000 North Korean dead. There were also an estimated 900,000 Chinese casualties. Half of Korea's industry was destroyed and a third of all homes.

Civilian casualties, WW2:

Civilian casualties in the United Kingdom, slightly over half of which were inflicted in the London area, were as follows:

                   Killed    Seriously injured    Total
Aircraft bombs      51,509          61,423       112,932
V-1 (flying bombs)   6,184          17,981         24,165
V-2                  2,754          6,523          9,277
Artillery fire         148             255            403
---------------------------------------------------------------
Total               60,595          86,182       146,777

Civilian casualties in the USSR have been placed roughly at 2,500,000 killed. The loss of population (including both military and civilian casualties) caused directly or indirectly by the war has been stated at 20,000,000. Air raids against Germany killed approximately 300,000 Germans and seriously injured about 780,000 more. Numerous additional casualties occurred during the Soviet invasion of 1944-1945, but no specific estimates are available. Japanese civilian casualties probably approached 500,000 killed and 625,000 seriously injured, plus a considerable number reported as missing after the fire raids and atomic bombings. In addition, about 360,000 Japanese captured by the Russians in Manchuria, Korea, and the Kuril Islands were still missing in 1950; a large number of them have never been accounted for. Chinese civilian losses are unknown but probably numbered several million.

Pile the bodies high at Austerlitz and Waterloo.        
Shovel them under and let me work—        
                I am the grass; I cover all.        

And pile them high at Gettysburg        
And pile them high at Ypres and Verdun.              
Shovel them under and let me work.        
Two years, ten years, and passengers ask the conductor:        
                What place is this?        
                Where are we now?        

                I am the grass.              
                Let me work.