In June of 1900, government of the Transvaal surrendered to British forces and victory celebrations took place. However, these were premature, as the South African War now entered a phase of irregular guerilla warfare with stubborn Boer Kommandos refusing to capitulate. As part of the ongoing operation to suppress these rebels, a column of British and Canadian troops under Major-General Smith-Dorrien set out on November 6, 1900, to destroy farms that had been sheltering Boer forces. On reaching a farm called Lilliefontein, however, the British and Canadian troops found that they had ventured into a countryside where the resistance was unexpectedly strong. The column commander therefore decided to pull back the next day to their safe base .
Mounted troops of The Royal Canadian Dragoons and a battery of Canadian artillery were assigned the task of acting as rearguard to hold off the enemy as the column pulled back. They soon found themselves hard-pressed, however, as hundreds of Boers charged, firing their guns from their saddles. The thin Canadian rearguard, spread out over an arc of one-and-a-half miles, acted with amazing courage, holding off the Boers long enough for the artillery to escape. As a final act of courage in this drama, Private William Knisley, seeing an unhorsed comrade hiding from the hail of fire behind an obstacle, rode forward despite the Boer fire and rescued his friend, although he was seriously wounded in the process.
It had been a remarkable fight, the Canadian troops showing themselves to be more than equal to the Boers in determination and fighting ability. Major-General Smith-Dorrien recognized this in his report to the British Commander-in-Chief, stating that he had "no praise too high for the devoted gallantry "shown by the men of The Royal Canadian Dragoons and Canadian Artillery. Lord Roberts was sufficiently impressed to award three Victoria Crosses for this single action, an unprecedented number for a single action in the war. Lieutenant Richard Turner, Lieutenant H.Z.C. Cockburn and Sergeant Edward Holland, all of The Royal Canadian Dragoons, received this prized decoration. Trooper Knisley of The Royal Canadian Dragoons was also recommended for the Victoria Cross but, instead, received the Distinguished Conduct Medal. Lieutenant E.W.B. Morrison of the Canadian Artillery received the Distinguished Service Order.
On the completion of his term of service, William Knisley returned to his father's small farm in southwest Ontario. However, he had always been a restless youth and, when the announcement was made that another contingent was being recruited, he jumped at the chance to return to southern Africa. The British were still unable to suppress the continuing Boer insurgency and, this time, Knisley joined the ranks of the 2nd Canadian Mounted Rifles.
West of Pretoria, in an area of low bush and hills with few roads, one of the most skilful Boer leaders, Kroos de la Rey, had gathered a Kommando of almost 4,000 with which he was attacking isolated British posts whenever an opportunity occurred. In order to put an end finally to these activities, a British force of 16,000 men, divided into a number of columns, was gathered and set in motion at the end of March 1901. As part of this campaign, the 2CMR was assigned the role of advance guard for a column of 1,600 men carrying out a reconnaissance to the south-west. At about mid-morning on March 31, the column suddenly came upon a Boer force that was stronger than expected. The British commander began setting up a fortified camp by the Little Harts River but quickly came under attack from three sides, with Boers charging the perimeter on horseback. The Boers continued their attacks on the main body for hours but could not break through the stubborn defence. The Boers finally broke off the action and withdrew before a British rescue force could reach the area. Except for Paardeberg, Canadians that day suffered the highest losses in the war - thirteen killed and forty wounded.
Unfortunately, William Knisley was with the column rearguard that day. When the column had come under attack, he and five other troopers found themselves cut off and unable to get back to the main camp. Instead, they choose to set off overland to try to get back to the main British base at Klerksdorp, over 100 km (60 miles) away. They fought their way through Boer country for, two days' in an attempt to reach their base. The Boers closed in on them, however, pinning them down on a rocky kopje. Here, the little band of Canadians managed to hold off their attackers for another day. The group finally surrendered after they had run out of ammunition but, by that time, Knisley and another man had been killed. The Boers paid their respects to Knisley by burying the Distinguished Conduct Medal he had won at Lilliefontein with his body.