Battle of Meridian

The Battle of Meridian was a conflict between UNSC and Covenant forces on the planet Meridian. The first "Mantis" prototype engaged in an action known as the "Cherbourg Run", in which it successfully engaged 18 heavily guarded Type-27 Anti-Aircraft Cannons, also known as "Mantis".

Aftermath
The success of the prototype in the "Cherbourg Run" is one of the theories of why it was eventually called "Mantis".