Has there ever been a tornado happen during a battle?

Yes ... there has been a tornado happen during a battle; the battle waged by the British in the nation's capital during the War of 1812 on August 25 1814.

Another battle where a tornado struck occurred during the Civil War on April 2 1862 in Bird’s Point ... Missouri and across the river in Paducah ... Kentucky.

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Category shifting idiot afoot.

That is a very interesting question; not that I know of, but there have been some interesting weather things take place during war.

In WWII General George Patton desperately needed aircraft strikes to support his army tank attacks. But they couldn't fly due to very bad weather. Patton asked his Chaplain officer to write a prayer for him, which of course he did. Patton went into the nearest chapel and prayed that prayer to God and within hours the bad weather subsided, the bombers came in and struck their German targets, providing Patton and his 3rd Army with a great victory.

This is completely true, check it out.

Like, on a battlefield, while the battle was going on? Dunno.