Surprise Attack is the 684th chapter of the Kingdom manga, written and illustrated by Yasuhisa Hara.
Summary
Gyoku Hou HQ
In a flashback to the previous days of the battle, Ou Hon tasks A Ka Kin with the assignment of climbing up from the right end in order to utilize a pincer on top of the cliffs. A Ka Kin says due to the terrain it won't be an easy task and even if they hurry it'll take 3 days at least. Ou Hon says he knows and that they'll meet up there in 3 days.
Right Side of Cliff
A Ka Kin's unit gets to the end and are analyzing their options. There's a path that's easier to climb a bit to the left but A Ka Kin says it's too close and that the Zhao are sure to have soldiers there so this is their only choice, and they must climb up in 3 days. Making their way up after losing a few soldiers and horses on the way they spot the Zhao but also sees that the Gyoku Hou had been defeated above the cliff. A soldier says maybe they should go down and save the soldiers they can below, but A Ka Kin says to wait and spots the Hi Shin Army. Ban You is annoyed because he realized A Ka Kin actually made it in time and just waited while Ou Hon and the rest of them were on the brink of being almost annihilated. Ten remembers his name and wonders if this was actually done by choice, he's either a really unreliable man or a genius who has a deep understanding of tactics.
Above the Cliff
A Ka Kin's unit is pushing in while the Zhao HQ is in trying to understand the situation. The Zhao soldier thinks Ou Hon must have sent them up in advance so they're probably a unit that is formidable, so he directs their left side soldiers to defend against A Ka Kin. Ten sees this and is surprised at the speed of their reaction. A Ka Kin says that it's a good thing they brought their horses and takes his soldiers towards the forest in the back. The Zhao were only infantry above the cliff so they couldn't catch up to them.
Hi Shin/Gyoku Kou HQ
At the HQ, they can't see A Ka Kin's unit anymore and some think he ran away. But Ten says that it's enough to pose a threat to the Zhao left and prevent them from going towards Shin and this gives him a chance to push into their HQ. Rei is getting a ride from Den Ei above the cliff and notices their speed went up by a lot. The HQ is shocked at their speed and Ten explains that right now if the Zhao escapes to the back A Ka Kin will be there and if they go down the cliff Kyou Kai is there so this is their best chance at winning this battle.
As the Hi Shin forces closes in, Gaku Haku Kou orders his soldiers to get ready, and he gets ready to meet the attackers. Then see how A Ka Kin's Unit was able to climb the cliff. During the climb multiple horses die, but A Ka Kin made sure to take additional ones, so that it didn't hinder their performance in any major way. After they got to the top, they see that the rest of Gyoku Hou Army didn't make it, but they've noticed the Hi Shin Army.
Back in the present Ban You and Ten are surprised about A Ka Kin's entrance. Ka Ryo Ten wonders whether he is someone who is not supposed to be trusted or a genius of battle. Seeing all the chaos, the Zhao sends part of their armies to anticipate A Ka Kin. His cavalry instead of attacking them directly just runs around in order to put psychological pressure. This greatly helps Hi Shin Army to push their advance as they almost reach the Zhao's HQ. The chapter ends with Gaku Haku Kou appearing before the Hi Shin's cavalry and making a swing with his mace.