A Route March is a march done in formation over any distance ranging from 20km to 70-80km depending on the Unit conducting it. They are done to a time limit - and it's always a tight one. Take yourself outside and do your fastest possible power walk without breaking into a run and you are close to the kind of pace we are talking about. A route march is designed to condition people to the physical demands of combat and test the physical fitness and readiness of both the individual and the unit.
Route Marches are often done wearing a dress code called Marching Order in the Australian Army.
Marching Order basically packs everything an individual and a unit are likely to need to fight and live for a minimum of three days unsupported in a combat zone. Food, water, shelter, sleeping gear, clothing, ammunition, medical supplies, communications gear, weapons, cooking gear, identification documents, notebooks - body armour when needed. Then you add any extra gear required by the mission and distributed throughout the unit for people to carry. Loads are carried by the individual in both a backpack and combat webbing. All of the load is on your shoulders and hips.
Marching order can weigh from 30kg all the way up to 70kg or more depending on mission requirements and the size of the individual carrying it. When I was a fit and young Army Officer my average "fighting weight" stayed at around 65kg - so even the lightest possible version of Marching Order was around 50% of my bodyweight. I trained with women a lot smaller than me. The big men didn't get out of it though. If a small person reached the designated percentage bodyweight limit their equipment (usually ammunition or food) would be redistributed for team mates to carry. If you weighed 120kg you'd get your full load and possibly part of someone else's as well. A 70kg pack is still over half the body weight of a man weighing 120kg.
If you want to know what that load feels like the safest way is to go to a gym and look at what a stack of 14 five kilograms weights looks like. Then ask yourself first - could you carry them all? And then - could you carry them at a fast power walk for 70km in 12 hours? Could you do it for 20km inside 2.5 hours? And then - could you do all of that on 3 hours sleep and short rations?
When you shoulder one of these loads the weight is crushing even when you shoulder it willingly. You often can't lift your head, so vision is restricted. If you fall you need help to stand. If you stumble you'd better hope someone can catch you, or you will know the taste of blood and dirt in your mouth when you face plant. You learn to fall on your side if you can, because if you put your hands out to stop the fall you risk a sprained wrist or worse. If you misstep in a pothole at that speed carrying that kind of weight, it is possible to break ankles or knees. You fall away from the line of march so you don't trip up your mates behind you - they can't stop or change direction quickly either.
When you reach the end of the march and are in a safe location there are only two words you want to hear:
Only someone who's done it knows that "lighter than air" feeling you get when you pop the clips on the shoulder straps and your pack hits the ground. When you no longer need it - you can't drop it fast enough. You know you'll have to pick it up again - but only for a little while. After 20km or more of being crushed into the ground at every step it can be tricky to readjust your balance when you are a carrying no weight at all. You get a little light in the head as your circulation re-establishes. You actually feel half clothed and kind of vulnerable without your weapon, your pack and your body armour.
When you no longer need your pack and your body armour - you drop it - and you feel as light as a feather.
I recently had a conversation with a veteran who is working hard to "unwind" his emotional armour and present a softer aspect to the civilians he now works with. He has recognised that aspects of his military conditioning and behaviours are no longer serving his interest in his new career. He is going through the process of sorting out which of his conditioned behaviours will still serve his interests moving forward, and which ones he can safely discard. It's not easy - but he's doing it anyway.