Stand facing the landmine with your feet shoulder width apart while holding the end of the barbell in your hands with your arms fully extended down towards the ground.
While keeping your torso tall and core engaged, step directly out to one side, using the foot you have stepped out with to sit down into the lunge while keeping your other leg straight.
Drive through your heel on your bent leg as your step together to return to the starting position.
Repeat for desired number of reps on the same side before switching sides.