The operation began on April 15, 1945. Canadian units moved out from their staging areas near Arnhem and advanced northwest through towns like Otterlo, Barneveld, and Voorthuizen. Major-General Bert Hoffmeister, commander of the 5th Armoured Division, emphasized the importance of speed. Intelligence reports indicated that German forces in the area were weak—poorly equipped, fragmented, and lacking armored support. 

Tanks from the British Columbia Dragoons and Lord Strathcona’s Horse led the charge through forests, over sandy ridges, and into Dutch towns. Initial German resistance was sporadic, but as the Canadians approached key routes that German troops relied on for retreat, the fighting intensified. Around Voorthuizen, Canadian forces faced mines, marshy terrain, and increasingly fierce German opposition, but they pressed on. 

On the night of April 16–17, a dramatic clash erupted in the village of Otterlo. Unbeknownst to German forces, the village now hosted the divisional headquarters of the 5th Armoured Division. Between 600 and 900 desperate German soldiers attempted to break through the village in a chaotic nighttime assault. What followed was a fierce and confusing battle in the dark. Canadian infantry from The Irish Regiment of Canada, artillery personnel, and even clerks and staff officers grabbed rifles to defend the headquarters. 

Supported by tanks and flamethrowers, the Canadians held their ground. By dawn, over 300 German soldiers had been killed and many more captured or wounded. The so-called "Battle of Otterlo" became one of the last major night actions of the campaign in the Netherlands, and a stark reminder that even in its final days, the war remained deadly. 

After Otterlo, the operation resumed its momentum. Canadian armored units advanced toward Putten and eventually reached the shores of the IJsselmeer. German paratroopers offered stiff resistance along the way, but the Canadians received crucial help from the Dutch resistance, who provided intelligence, guided the troops through safe routes, and in some cases fought alongside them. 

On April 18, Canadian troops liberated both Putten and Harderwijk. A handful of German units attempted to escape across the IJsselmeer by boat, but many were intercepted by machine-gun fire or even direct hits from Canadian tank shells. The escape route was sealed. 

In just four days, the 5th Canadian Armoured Division had covered vast territory, captured thousands of German troops, and shut down vital enemy withdrawal paths. Civilian casualties were minimized, and Canadian losses remained relatively light thanks to swift movement and close cooperation with the Dutch underground. 

By April 19, 1945 the Canadians handed over the liberated region to the 1st Canadian Division. Operation Cleanser was complete. It marked a turning point in the campaign to liberate the northern Netherlands, and delivered a decisive blow to the retreating German army. The road to full liberation was now wide open.