They nodded their heads in unison.
Many states and the Xirong Empire eyed the valley's large freshwater lake and its waterways, which led into the vast, gushing Yellow River. Water was a scarce, yet precious resource inland. Waterways had a use as a shipping way for transporting supplies or even troops.
"Anyone who wants to control the waterways has to control the valley, but their biggest obstacle is the surrounding mountain range," Halun said. "No one could conquer this valley because of that range."
The surrounding mountain range of the Black Mountains acted as a natural fortress against invading armies. Narrow high altitude passes thinned down large armies and made them vulnerable to ambush.
The danger of avalanches and falling boulders could wipe out an army in minutes. Natural murder-holes and ledges acted as ambush hiding spots for defending archers.
"There're also the hidden mountain villages," Lieshan said. "The villages know the layout around. Most have their own militia, and many are skilled martial artists."
A large population of people lived in hidden hard-to-reach villages within the area of the valley at the base of the Black Mountains.
The residents owed no loyalty to no state or empire.
Most are members of martial arts sects and some underworld syndicates who refused to pledge allegiance to any state or empire fled to the Black Mountains.
Those were skilled opponents in group fights and ambush.
Other residents of the Black Mountains also included descendants of outlaws or refugees looking for a safe place to shelter. Those were the worst to fight. Like a cornered animal had nowhere to run, they lashed out with ferocity.
"My state suffered heavy losses on the last try a decade ago. My older half brother and over ten thousand men lost their lives in a week when they tried to conquer the Black Mountains," Lieshan added.
Yinyue knew that was the reason the Dayan Emperors were reluctant to push past the Black Mountains to expand their territory. Too much effort and too many lives wasted on a valley with an uncontrollable population — lessons learned from other states foolish enough to try.
"Did they use cataphracts?" Kelian asked.
Lieshan narrowed his eyes at the clueless Kelian.
"Cataphracts are best used on flat ground, but no one uses heavy armor cavalry on mountainous terrain," Yinyue replied.
"Why not?" Kelian tilted his head.
A snort escaped from Halun, who pursed his lips into a thin line, struggling from the urge to burst out laughing. He glanced at the masked Yinyue, curious about the Grand Prince's hidden facial expression.
Unlike Lieshan and Yinyue, both Halun and Kelian never fought in major battles. Let alone use cataphracts.
Halun took part in the occasional border clashes with the neighboring states — a couple of yelling from each side, a few arrows shot, and a half-hearted siege of a fortified border town.
He wondered if Kelian was pretending not to know or had never experienced leading troops. Then again, no one wanted Youyu's arid barren borderlands. Only reason to invade Youyu was for their copper or tin mines deep within the interior of the state.
"Imagine a horse wearing heavy metal armour and carrying a man with heavy armour climbing up the mountain," Lieshan said in a condescending tone, like an old scholar teaching a young child. "Then they charge at full speed. But there's a ravine ahead. No time to stop the horse…so what happens?"
"They fall into the ravine…," Kelian replied. "But why would they charge?"
Lieshan threw his arms in the air and turned to Yinyue. "Want to try explaining to him about how cataphracts work?"
Yinyue stared at Kelian and sighed. "Cataphracts need to charge at full speed for maximum effectiveness. If you wish to see how it works, I can send 5000 of my cataphracts to your border for a demonstration."
Color drained out from Kelian's face and he shook his head to refuse the offer. He heard stories of cataphracts charging but he didn't want the experience of facing cataphracts.
"Shouldn't you be worried about the Xirong conspiring with Gaoyang to take the Black Mountains?" Lieshan asked Yinyue.
Yinyue shook her head. Not worth worrying over a rumour. Any talk of alliance needed time to negotiate, and many covert methods existed to sabotage those negotiations.
Other states around won't sit around, doing nothing. Especially Lieshan's.
Lieshan hated the way Yinyue answered. He preferred the chattier nobles who spilled more than they should. The more they speak, the more clues he can could grasp from their many words to figure out their intentions.
The quiet ones, like Yinyue, kept their real thoughts from everyone. And when they spoke in serious conversations, they answer in riddles. To him, Yinyue was very unpredictable, hence dangerous.
He stole a look at the masked Yinyue. Smaller and shorter than them, the Grand Prince seemed like a child demon under a mask. Never once had Yinyue removed the mask in their presence since their first meeting two years ago.
He wondered what face laid beneath the mask — a scarred one, or a hideous one, perhaps? This Grand Prince had been out in battles since eleven.
Can't be. The Dayan Empire disqualified princes with facial disfigurement, or any outward signs of disability from ascending the throne.
Yinyue's eyes pierced through his like a deep pool of empty darkness, reaching out to drag his soul to hell. A chill ran up his back.
These eyes belonged to a cold-blooded mass murderer.
"Like my eyes?" Yinyue asked.
He turned aside to avoid the sinking sensation and saw the two other princes shifting their bottoms in the cushion seatings on the floor, unnerved.
"No, um…something got into my eyes," Lieshan said while pretending to rub them with his sleeves.
A polite cough helped to clear the awkward air.
"Um…got any more details on this route proposed by Gaoyang state and the Xirong Empire?" Kelian asked.
The cooperation between Gaoyang state and the Xirong Empire, if true, may pose a threat to Youyu state, which shared a border with Gaoyang.
Halun folded his arms. "That worried, huh?"
"You know my state is the poorest…," Kelian replied.
'Poorest' was a diplomatic word for the weakest. Weak states, like Youyu, had no choice but to ally with a bigger neighbouring state, like Taotang to survive. The reason the Youyu state allied with Taotang state is to avoid being swallowed up by Gaoyang.
Halun pointed at Yinyue. "Kelian, that's whom you should fear."
Yinyue rolled her eyes.
Kelian raised his hands in the air and said to Yinyue, "If you come, just give me a notice so I can surrender. We'll just leave our border city empty for your troops to occupy."
She chuckled and gazed out the window at the waterfall without an answer.
"Grow a damn SPINE!" Lieshan retorted in disgust at Kelian's words.
"My state doesn't stand a chance against the Dayan or Xirong cataphracts…I'm being realistic," Kelian replied.
He heard about what Yinyue did with Gaoyang's border city of Luoran — the former city. It ceased to exist.
No point facing the Dayan cataphracts which could mow through their troops, like a sharp metal cleaver slicing through meat, and trample his tiny state down to dust in a day. No chance of survival equated to no point in fighting.
"I won't attack your state if I have no reason to," Yinyue replied.
"Then um…why attack Luoran? That attack could be the reason Gaoyang went to seek Xirong cooperation," Kelian asked.
Yinyue sipped the tea from her cup while they waited for the answer. She didn't care if Gaoyang went to the Xirong Empire to cry about one miserable city.
If she knew anything about the Xirong Empire — they didn't care about whiny states but the benefits of working with those states.
Yinyue glanced at the others. No doubt, Gaoyang held responsibility for spreading fake rumors to stir up uneasiness between the states and the Dayan Empire. Her spies kept her updated on rumours, ranging from believable to the ridiculous.
The rumors created paranoia by spinning tales of how the Dayan Empire planned to taking over the states and tested the defences of Gaoyang first.
More lies than the truth to stir up suspicion in their neighbours. Yinyue planned on returning Gaoyang's courtesy tenfold.