Jochi’s men formed under his orders into the widest line the land would allow, the rest assembling in a block behind the warriors with the heaviest armour. Jochi could see spears and bows ready in the Arab ranks, though he was disappointed they had not brought elephants with them. The Arab princes seemed very attached to the idea of elephants in warfare. In return, the Mongols enjoyed sending them wild with arrows, then delightedly watching them trample their own troops.

Jochi looked down into the valley, judging the steep slope he would descend. It was criss-crossed with wild goat tracks, but scrub grass grew and the horses would fare well charging on such soil. He glanced left and right along the lines as he took his position in the very centre of the front rank. His bow would sound with the first volley and he felt the swelling confidence of men around him as they stared down at the army marching stolidly towards them. The Arabs blew horns and crashed drums as they marched, their horsemen visibly nervous on the flanks. The sloping ground was already compressing them and Jochi thought they had to be led by some young fool promoted for his blood rather than talent. The irony of his own position amused him as he gave the signal to walk the ponies down the central defile. There could be very few sons of kings or khans who led despite their fathers rather than because of them.

As his tuman moved to a slow trot, Jochi constantly scanned the lines, looking for flaws. His scouts were out for many miles, as Tsubodai had taught him. There would be no ambush, no sudden appearance of reserves. Whoever led the force to relieve Samarkand had treated the Mongols too lightly and would pay for it. Jochi blew a single note on the horn around his neck and saw the heavy lances brought out of saddle cups, held now only by shoulders and arms trained to iron strength. As he increased the speed to a canter, Jochi nodded to a flag-bearer and watched the order to widen the line stretch across them. For this moment, he had practised and practised until the men’s hands were bloody from shooting arrows at the gallop or punching lance points into straw targets a hundred times a day.

The army they faced loosed a volley of shafts on a barked order. Too early, Jochi thought, watching half of them fall short while the rest skipped uselessly off shields and helmets. He moved into a smooth gallop then and he could not have held back his men if he had wanted to. He put aside his nervousness and let the rhythm of his mount control his movement as he stood in the stirrups and placed a shaft on the cord.

All along the Mongol lines, men followed suit. The lancers began to dip the points, judging the moment when they would strike and kill.

Jochi released his arrow and six hundred more followed it on the instant. As they reached for another, the lancers dug in their heels and came together as an armoured spike, lunging ahead of the rest. They hit at full speed and went through or over anything they touched, ripping a hole like a red mouth. Those behind could not stop and Jochi lost sight of falling men as he was carried deep into the enemy, bending his bow once more.

Ahead of him, his lancers threw down the shattered poles and drew swords as one. The archers behind them loosed another volley to the sides, widening the hole and driving men back as if burned. It was the best use of lances and bows Jochi had found and he exulted at the destruction they had wrought in just a few heartbeats. His rear lines rode out wide to overwhelm the wings, the tactic almost the reverse of his father’s favoured horn manoeuvre. In just instants, the head of the enemy column boiled, all order lost as it fell back on itself.

Jochi drew his own sword as his mount came almost to a stop, unable to press any further through the ranks facing him. He could feel the moment was perfect for the flank attack and looked up for his brother. He had time only for a single glance at the steep left flank before he was defending desperately, knocking aside a spear point that threatened to sweep him off the saddle. He looked again, not believing, yet Chagatai’s tuman remained where it was on the slope.

Jochi could see the figure of his younger brother quite clearly, sitting his horse with relaxed hands resting on the saddle horn. They had not arranged a signal to bring him into the flank, but Jochi blew his horn anyway, the note ringing over the heads of his men. They too saw their kinsmen standing still and those who did not understand gestured furiously for them to join the fight before it turned.

With a curse, Jochi let the horn fall loose, fury filling him so that the next two strokes seemed effortless, his strength surging in his right arm. He wanted it to be Chagatai as he caught a man in the joint between his armour and neck, gashing him terribly as he fell beneath the hooves.

Jochi stood in his stirrups once more, this time searching out a way to free his men from the crush. The odds were good that he could disengage, with the front ranks still embroiled in the horns of his finest warriors. If they had not been betrayed, they might have fought clear, but he sensed the shock running through his men and it cost them in lives. The enemy had no idea why a Mongol general would sit and do nothing, but they were quick to take advantage.

Jochi called orders in frustration, but the Arab cavalry widened its line, arcing heavy horse ranks up to the rising ground and then hammering back down against his beleaguered men. Even then, they did not dare to pass too close to the left flank, where Chagatai waited to see Jochi butchered. In breathless moments between blows, Jochi could see senior men remonstrating with his brother, but then he was swept back into the fight.

His own officers were looking to him to call for a retreat, but Jochi was filled with fury. His arm ached and his father’s sword had lost part of its edge on armoured men, but he felt berserk rage fill him and everyone he killed was his brother or Genghis himself.

His men saw that he no longer looked to the hills. The son of Genghis fought with his teeth bared and his sword arm swung lightly as he dug in his heels and sent his pony over dead men. They grinned to see his lack of fear and followed with a howl. Those who were cut ignored the wounds, or did not feel them. They too were lost for a time as their blood responded. They had pledged their lives to Jochi and they had ridden an army into the ground. There was nothing they could not do.

His Chin soldiers fought with insane intensity, cutting their way deeper and deeper into the enemy column. As the Arab cavalry impaled them with spears, they grabbed the weapons, pulling the riders from their mounts and stabbing wildly as both men died. They would not turn from the swords and arrows of the enemy with their friends in ranks around them. They could not.

Under the relentless pressure of madmen who grabbed with bloody hands at swords that killed them, the Arabs turned and broke, their fear rippling even to those who had not yet joined the fight. Jochi saw one of his Chin officers wielding a broken lance as a club, stepping over dying men to smash it into the face of an Arab on a fine stallion. The Arab fell and the Chin soldier roared in triumph, calling a challenge in his own language to men who could not understand. The Mongols laughed to hear his bragging tone and fought on as their arms became leaden and wounds sucked at their strength.

More and more of the enemy turned from the ferocious attack and Jochi was blinded for a moment by a spray of blood across his eyes. Panic filled him at the thought of being hit when he could not see, but then he heard Chagatai’s horns moaning across the valley, followed at last by the sound of thunder.

Chagatai’s tuman struck an enemy already desperate to get away from those who assailed them. Jochi watched panting as a space cleared around him and fresh shafts tore into the fleeing Arabs. He saw his brother again for an instant, riding like a king before he reached the foot of the valley and vanished from sight. Jochi spat hot phlegm, his battered body aching for the blow he wanted to land on Chagatai’s neck. His men knew what had happened. He would be hard-pressed not to have them pick fights with those who had stood and watched in safety. Jochi swore to himself as he imagined Chagatai defending the delay, words like sweet grease in his mouth.