Honestly really disappointing that the battle between Ousen and Riboku, two of the greatest strategists/tacticians of all time in China and two of the big four in the warring states period, boils down to "uh lol we're gonna smash our armies against each other, Riboku has a super saiyan btw". It's just fucking fantastical that the very first battle we got where Shin didn't even know what was happening had more actual tactics and clear goals that aren't just "run at the enemy in a straight line". This is absolutely embarrassing compared to the Ouki battle, or the five hills, or even the Gyou campaign. I'm convinced that the author just wrote himself into a corner and feels the need to make Riboku obviously superior to Ousen so all he can do is give Riboku a fucking shinigami captain to single-handedly kill half of Ousen's central army.
Do you really think it's easy without pikes and on foot facing a 40-50 foot cavalry that is tall enough to step onto your shoulders and crush it with ease through sheer weight? Now, imagine that is charging at you with a skilled rider wielding a bigger than average glaive that can probably cleave a modern car in half. With a spear that's probably both of your arm length and was not made to withstand a charge of any kind. Imagine all that massive flesh wall just charging at you with a chance to behead you from above.
It is, actually. Literally the single worst place for cavalry to be was bogged down on all sides by heavy infantry in close formation (aka the exact scenario most cavalry tends to be in, in this manga). The fact is that for every horseman there's eight infantrymen, numbers alone kills you here. People just didn't do what Shibashou is doing. You can plow into infantry, but the infantry can't be in close formation and standing their ground. These infantrymen could have axes for all the difference it would make.