greenfire there were several huge battles in the American Civil War with some astonishing casualty rates. Not to mention it tore up families. Brother versus brother, cousin vs cousin and so on. I've read up a lot on the Civil War and have never come accross a battle with a forest fire, but hey, I can always check again.
The ten costliest land battles, measured by casualties (killed, wounded, captured, and missing) were:
<TABLE =wikitable>
<T>
<TR>
<TH>Battle (State)</TH>
<TH>Date</TH>
<TH>Confederate
Commander</TH>
<TH>Union Commander</TH>
<TH>Conf. Forces</TH>
<TH>Union Forces</TH>
<TH>Victor</TH>
<TH>Casualties</TH></TR>
<TR>
<TD>Battle of Gettysburg
(Pennsylvania)</TD>
<TD>July 1â€"3, 1863</TD>
<TD>Robert E. Lee</TD>
<TD>George Meade</TD>
<TD>71,699</TD>
<TD>94,589</TD>
<TD>Union</TD>
<TD>51,112
U: 23,049
C: 28,063</TD></TR>
<TR>
<TD>Battle of Chickamauga
(Georgia)</TD>
<TD>September 19â€"20, 1863</TD>
<TD>Braxton Bragg</TD>
<TD>William Rosecrans</TD>
<TD>75,357</TD>
<TD>61,753</TD>
<TD>Conf.</TD>
<TD>34,624
U: 16,170
C: 18,454</TD></TR>
<TR>
<TD>Battle of Chancellorsville
(Virginia)</TD>
<TD>May 1â€"4, 1863</TD>
<TD>Robert E. Lee</TD>
<TD>Joseph Hooker</TD>
<TD>60,892</TD>
<TD>133,868</TD>
<TD>Conf.</TD>
<TD>30,099
U: 17,278
C: 12,821</TD></TR>
<TR>
<TD>Battle of Spotsylvania Court House
(Virginia)</TD>
<TD>May 8 â€"21, 1864</TD>
<TD>Robert E. Lee</TD>
<TD>Ulysses S. Grant</TD>
<TD>52,000</TD>
<TD>100,000</TD>
<TD>inconclusive</TD>
<TD>30,399
U: 18,399
C: 12,000</TD></TR>
<TR>
<TD>Battle of Antietam
(Maryland)</TD>
<TD>September 17, 1862</TD>
<TD>Robert E. Lee</TD>
<TD>George B. McClellan</TD>
<TD>65,000</TD>
<TD>82,654</TD>
<TD>Standoffâ€"kept England out</TD>
<TD>23,134
U: 12,410
C: 10,724</TD></TR>
<TR>
<TD>Battle of the Wilderness
(Virginia)</TD>
<TD>May 5â€"7, 1864</TD>
<TD>Robert E. Lee</TD>
<TD>Ulysses S. Grant</TD>
<TD>61,025</TD>
<TD>101,895</TD>
<TD>inconclusive</TD>
<TD>28,666
U: 17,666
C: 11,000</TD></TR>
<TR>
<TD>Second Battle of Bull Run
(Virginia)</TD>
<TD>August 29â€"30, 1862</TD>
<TD>Robert E. Lee</TD>
<TD>John Pope</TD>
<TD>48,527</TD>
<TD>79,862</TD>
<TD>Conf.</TD>
<TD>25,251
U: 16,054
C: 9,197</TD></TR>
<TR>
<TD>Battle of Stones River
(Tennessee)</TD>
<TD>December 31, 1862</TD>
<TD>Braxton Bragg</TD>
<TD>William Rosecrans</TD>
<TD>44,330</TD>
<TD>54,448</TD>
<TD>Union</TD>
<TD>24,645
U: 12,906
C: 11,739</TD></TR>
<TR>
<TD>Battle of Shiloh
(Tennessee)</TD>
<TD>April 6â€"7, 1862</TD>
<TD>Albert Sidney Johnston
P. G. T. Beauregard</TD>
<TD>Ulysses S. Grant</TD>
<TD>44,968</TD>
<TD>65,085</TD>
<TD>Union</TD>
<TD>23,741
U: 13,047
C: 10,694</TD></TR>
<TR>
<TD>Battle of Fort Donelson
(Tennessee)</TD>
<TD>February 13â€"16, 1862</TD>
<TD>John B. Floyd
Simon Bolivar Buckner, Sr.</TD>
<TD>Ulysses S. Grant</TD>
<TD>12,110</TD>
<TD>20,057</TD>
<TD>Union</TD>
<TD>19,455
U: 2,832
C: 16,623</TD></TR></T></TABLE>