During the years 1941 to 1945 the property was used as a German prisoner-of-war camp. The camp was used primarily for German officers, with over 800 prisoners occupying the camp at times.

Prisoners of war (POWs) were paid and could receive promotion in rank while interned. With their pay, POWs could purchase goods. The soldiers were kept occupied by various activities including lectures, a symphony orchestra, a camp newspaper, sports, film shows, games, gardening, and the farm operation.

The most striking change made to the school during its transformation to a prison camp, was its enclosure by a double-wire perimeter fence with gates and guard towers. Although, prior to the war, the school was technically a correctional institution, the design of school and campus expressed the ideals of voluntary participation and non-enclosure, principles that could no longer stand when it became a de-facto prison during the war. Landscape elements such as old trees, which had helped to beautify the landscape, were cut down because they obscured guards’ views from the towers. Outside the double-wire perimeter, barracks and other utilitarian wooden buildings were constructed for Camp 30 personnel. Kiwanis House served temporarily as the headquarters for staff. Roads around the school were cleared for easy access to the site.

Camp 30 opened in November 1941, and by the end of its first month of operation, there were a total of 544 prisoners of war interned there.48 Partitions were added in the Triple Dormitory (known as Haus IV) and Kiwanis House to accommodate some of them.49 The Infirmary building was modified to house high ranking officers and was renamed the General’s House. Jury House became an officers’ dormitory. The Natatorium continued in its recreational function. As the war progressed and more enemy combatants were captured and transferred to Bowmanville, two wooden barracks were constructed inside the perimeter fence in order to avoid overcrowding: a U-shaped building adjacent to the cafeteria, and an H-shaped building between the U-shaped building and Jury House.

After Camp 30 was closed in April 1945, the purpose-built barracks inside and outside the fence were dismantled, the guard towers and wire perimeters were torn down, and the school buildings were repaired. Materials from the dismantled barracks were taken to a new site, now Veterans Avenue in Bowmanville, and used to build Victory Houses for returning soldiers. After damages were repaired, the property was returned to the Province of Ontario. In 1947, the school resumed its pre-war activities.

The best-known single event associated with Camp 30 is the Battle of Bowmanville, a three-day prison riot over the shackling of prisoners at the camp. This event was part of the larger international shackling crisis which began immediately after the raid on Dieppe in August 1942. When the German government discovered operational orders that directed British and Canadian troops to handcuff their prisoners in order to prevent them from destroying documents, it threatened to handcuff all Allied captured soldiers at Dieppe. The crisis escalated when German prisoner of war were shackled and killed by British forces during the raid on the Island of Sark in October 1942. In response, German authorities handcuffed some 1,376 Canadian and British prisoners of war held in Germany. The British threatened to raise the number of shackled German prisoners, and when Germany nearly tripled the number of chained Canadian and British prisoners, the British government requested that German prisoners of war in Canada be shackled.

After debate in Cabinet, the Canadian government acquiesced Camp 30 (Bowmanville) along with 3 other POW camps were chosen to implement the request. At Bowmanville, when attempts were made to shackle POW’s, a riot broke out, with the prisoners using makeshift weapons and barricading themselves inside several buildings within the enclosure. The greatest number of protesters positioned themselves in the Cafeteria. Canadian Lieutenant G.E. Brent, was taken hostage and German prisoners held off rescue attempts by using baseball bats, umbrellas, and stones. After three days, internment authorities eventually suppressed the insurrection with the help of troops from Barriefield and high-pressure hoses.

Part of the ongoing role of a POWs is to escape. Many plots and attempts were made none successful.  One memorable attempt was the challenge between the various houses to tunnel under Lamb’s Road, only to be discovered just before completion.  In 1942 one prisoner, a Luftwaffe pilot named Hans Krug escaped (but not by way of the tunnel) and managed to sneak into the United States before being arrested in Texas and returned to Canada.