A mongolian horse would more or less be ideal for the military, and it was used by the Mongolians to conquer like 1/4 of the world. They don't need to eat or drink very much, living in the harsh conditions of the desert, and frequently lose up to 30% of their weight in the winter, every year, suggesting their tolerance to extreme environments. A 250 kilogram mongolian horse can carry an additional 300 kilograms on it's back, essentially the weight of a horse on it's back, more than it's own body weight, and can carry up to 2000 kilograms in a cart behind it. They are quite small in comparison to many western race horses, around 400-800 pounds, vs. 2000+ pounds, and don't need to eat nearly as much, making them more ideal for transport and to reduce constraints on logistics. They have been bread for battle over the many centuries, and thus are not as easily scared out of battle then many horses. They are ideal for endurance, and long distance travel, and can go very long periods of time without food and water if cut off from supplies, and can forage for most of their food. They do well in both the freezing cold of the Mongolian deserts and the extreme heat, making them viable in nearly all environments. Their smaller size is also useful when traveling over rougher terrain, as they sink in to the ground less. They would be useful for specific purposes, like crossing the desert or other areas vehicles have a tougher time traveling, but not as a complete replacement for vehicles. One big use is in mountain warfare, where it's extremely difficult to use vehicles. To this day donkeys are still used by the Americans in mountain warfare, and horses like this would be a good replacement.
As for a modern use of horses xD "At the beginning of Operation Enduring Freedom, Operational Detachment Alpha 595 teams were covertly inserted into Afghanistan on October 19, 2001.[207] Horses were the only suitable transportation for the difficult mountainous terrain of Northern Afghanistan.[208] They were the first U.S. soldiers to ride horses into battle since January 16, 1942, when the U.S. Army’s 26th Cavalry Regiment charged an advanced guard of the 14th Japanese Army as it advanced from Manila". For very specific infiltration purposes, horses do a good job. They are typically quiter and lighter weight than a vehicle with comparative range and terrain coverage, capable of leaping over obstacles that even a tank would have trouble clearing. Air transported horses, in small aircraft, would make a lot of sense, especially since you could find most of the feed you needed from the environment. However that being said, it's not really ideal for, most purposes. One thing you do see horses used a lot for is police work in heavily urbanized areas, as they more easily move around traffic in congested areas. So for urban patrols, they might actually be useful.
I am here, simply to have a discussion. Also I don't understand how an obsession with armor is narcissism. "This also explains your blatant dishonesty, your constant projection about semantic arguments, your disproportionate hostility to criticism, and your 
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