Battle of Eclipse (-632 P.D.E.): The first and only attempt by the Crystal Empire (expanding south) to seize territory from the Republic of Equestria (expanding north) began and ended with the Battle of Eclipse, in which the hitherto-undefeatable crystal unicorn ability to lase (which, when grouped into phalanxes, permitted them to reduce fortifications and eliminate close formations in a matter of seconds) was countered by the emergency measure - proposed and implemented by the collegium caelis1 - of moving the moon and the sun in syzygy, producing an eclipse lasting three days to take away the ambient light upon which this ability depended.
The peace talks that followed were short, and defined the solution to the problem of the irresistible force meeting the immovable object. To wit, don't.
Why does just about every sci-fi work involve biological lasers, anyway? I have to say this is a new usage, though.
Have I said I love how absurd this planet's biology is?