From the Super Mario Wiki
Explosive Troops is the first level in Bowser's Castle (West) in the Bowser Jr.'s Journey mode of Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey.
This level has four battles. All rounds have a Bomb Boo in the center, which in the second and fourth rounds is under the effects of Malatone Formula:X. The first three rounds all have Spinies in a square formation and different explosive types at the very top and bottom, which switch places in the fourth round. Additionally, this is the only level in the game to feature Alarm Bob-ombs.