Dusaboss is quite on point about in his last post.
Protein powder has some strange reputation that somewhat prevents a scientific debate on the topic.
Most protein powders are made from Whey, which again comes from milk. Thats right, protein powder is milk protein in its highest quality.
As for why people then choose to drink protein powder instead of milk, the reason is simple: To get the same amount of protein from a "standard" protein shake (about 2 dl if dissolved in water, depends on how thick you like the shake), you will have to drink about 1 liter of milk, which is quite a lot and 1 liter of milk containt quite a lot more calories than the standard protein shake.
Protein powders offers a convenient and cheap way of getting protein into your diet, but the question is. However, there is a lot of protein hype these days and the industry tells you that you have to eat shitloads of protein.
Of course a Mr. Olympia needs a lot of protein. Considering he weighs around 140-150 kg and is full of muscle and drugs.
Usual recommendations for strength athletes is about 1,5-2g pr kg bodyweight. For a person that weighs 80 kg thats 120-160g protein each day. Considering that a soldier is not a strength athlete but maybe something in the middle (endurance + strength) and considering that a soldier might do a lot of work that does a lot of muscle breakdown (working days with little or no food for example) i guess about 1,5 g pr kg bodyweight or maximum 2g pr kg bodyweight is more than enough. Even tough studies on endurance athletes dont find a huge need for protein in great numbers at all.
As for protein powder for recovery thats mainly bullsh*t. Earlier scientific work thought there was a "anabolic window" the first 30-60 minutes post-exercise. Newer scientific works puts the "anabolic window" to a lot more than that, even up to 48 hours post-exercise. However, eating around the exercise times seems to have a little more effect (Eating 1-2 hours before and after workout shows a little better results vs eating 4 hours before and 4 hours after exercise). However, the total energy intake during the day is the most important dietary factor after you have done your exercise.
In my opinion protein powder is a great tool for those who needs it. If you are a strength athlete and have had a day with a little low protein intake because maybe you wasnt hungry that day or didnt have time to cook your meals, go ahead, toss in a shake. Whey protein is one of the best protein sources with the highest bioavailability. The problems occur when people substitute food and drink shakes instead, because food generally will give you more than just protein.
If you believe you need protein powders or supplements you either
a) you have a bad diet and should fix it
b) You dont have the ability to critical reflect your personal nutrition needs and your beliefs are based on what the industry tells you
Get some basic understandings on nutrition, know what you eat and if you calculate during the day that your protein take has been a little low, a shake might be okay. But if shakes becomes a staple for your protein intake you do something wrong. Eat animals and you will probably get enough protein.
As for health, there is little evidence that a generally high protein intake is dangerous, either if the protein comes from shakes (which as i said basically is milk proten) or other sources of protein.