That sort of troop massing is effective against small arms, but hopelessly vulnerable to Molotov cocktails, amonia+bleech/baking soda vapors, gasoline pits, etc.
Which is to say that the tactics being trained are effective only for peacetime operations, not urban war.
Yep. And also to a shotgun blast to the upper legs (Thighs) which would blow away the Femoral Arteries and ... well ... kill them ... within a minute. The BP drop is almost instantaneous. Or so I hear :-)
Not that I would do that, just sayin'. As I'm a peaceable person and don't even own a shotgun.
'Body Armor' is good and protects vital organs, but it won't stop you from getting killed.