The weeks before Nooitgedacht had been grim for the British. Lord Roberts had captured Pretoria in June, and the conventional war seemed won, yet the Boer commandos refused to surrender. Instead, they turned to guerrilla tactics in the valleys and ridges of the Magaliesberg range. Clements had been harrying the Boers in the Moot, the broad valley running through these ancient mountains, but the British were growing careless. On 2 December, De la Rey's commando ambushed an ox-wagon convoy east of Rustenburg, killing and wounding 64 British soldiers, capturing 54 men and 118 wagons. De la Rey's deputy, the young Jan Smuts, narrowly escaped death when a bullet meant for him killed another Boer instead. The raiders took the boots and clothing they needed, burned the rest, and released their prisoners. It was a sign of what was coming.

De la Rey spent three days scouting the British camp, studying its vulnerabilities. The position at Nooitgedacht had good water and could communicate by heliograph with Major General Robert Broadwood at Rustenburg, but the mountain looming above it was a fatal weakness. When General Beyers arrived with a 1,500-man commando, the Boers had numerical superiority and a plan to match. They divided their force into three striking columns: Beyers would lead his men up the mountain to overwhelm the 300 British pickets on the summit, Commandant Badenhorst would hit the camp from the west, and De la Rey would seize the kopjes in the Moot to the south, cutting off the British retreat. If each column succeeded, Clements's entire brigade would be encircled and destroyed.

The attack came in the pre-dawn hours. On the mountaintop, the fighting was visceral. Deneys Reitz, a young Boer combatant in Beyers's commando, described the moment the assault turned into a headlong charge: 'Stung by their cries our whole force, on some sudden impulse, started to its feet and went pouring forward. There was no stopping us now, and we swept on shouting and yelling, men dropping freely as we went.' After about 100 casualties, Captain Yatman surrendered the summit around 7:00 am. British reinforcements climbing the mountain walked into devastating fire from above. Meanwhile, fog had settled over the valley, too thick for the heliograph to flash a distress signal to Broadwood. Clements was entirely on his own. De la Rey and Smuts captured nearly every kopje in the Moot, but one position held: Yeomanry Hill, also called Hartebeestfontein. Clements concentrated his surviving troops there with remarkable speed, and by 8:00 am the British had driven back a Boer probing attack and were fortifying the hill. Soldiers even managed to drag a heavy 4.7-inch naval gun downhill and haul it into position.

With the mountaintop secured, Beyers needed his men to press the attack on the remaining British position at Yeomanry Hill. But the Boer fighters had discovered the British camp, and its stores proved irresistible. Months of deprivation in the field had left the commandos desperate for clothing, boots, and food. Deneys Reitz summed up the scene with wry honesty: 'We were refitted from head to heel.' Nothing Beyers could do would drag his men back to the fight. De la Rey's troops eventually joined the looting. At 4:00 pm, Clements gathered the remnants of his brigade and marched out toward Pretoria with his artillery, virtually unopposed. Half his brigade was lost to death, wounds, and capture, yet the core survived because the Boers chose plunder over pursuit.

The aftermath was paradoxical. Clements had suffered a humiliating defeat, losing half his brigade because he chose a campsite beneath an enemy-held mountain. Yet within a short time, a column under his command was again operating in the Moot, harassing the very commandos that had just beaten him. The British Empire's resources were simply too vast for any single Boer victory to be decisive. For the Boers, Nooitgedacht was a tactical triumph undermined by indiscipline. The battle demonstrated both the extraordinary courage of the commando fighters and the structural weakness of a guerrilla army that could not enforce orders when easier prizes beckoned. Today the Magaliesberg range still rises above the farmland northwest of Johannesburg, and the valley of the Moot looks much as it did when two armies clashed here on a hazy December morning in 1900.