Water Jet Tank

Often, a military will find itself in a situation where the enemy don't stand around in the open dressed in bright, easily identifiable uniforms waiting to be shot*. Irritatingly, the enemy takes to hiding behind things and in buildings, and not nicely decorated castles** either.

Water jet cutting is pretty interesting. Often water alone fired at 10,000 PSI at concrete will neatly cut through it, it works like soil erosion, only massively speeded up. The upping the pressure toward 40,000 PSI and adding a cheap abrasive substance, silicon carbide, quartz etc, takes water jet cutting to the next level, much faster and it will slice right through steel.

Typically water jet cutting is done at close range, 3-5cm or so. With more power, we can make this longer range. Typically, high-velocity water jets get disrupted & diffused by interactions with air. However, we can for example, have the high velicity stream shielded inside a fast moving air stream, or perhaps another ring shaped water jet.

So, now we have a tank that can drive up to a building and cut neat slots/door ways out of walls. We don't have to use indiscriminate explosives and potentially collapse buildings while leaving rebar intact.

* Very unsportsmanlike behaviour, civilization definitely took a downturn when Britain/France had to change into drab uniforms. I blame the Germans for not getting the whole arrangement and adopting hard-to-see Feldgrau.

** Castle sieging, sporting behavior.