During the Second World War Rée joined the Special Operations Executive (SOE). He also encourged his friend Francis Cammaerts to join the SOE. Given the code name "César" he was sent to occupied France in April 1943 as part of the Acrobat Network. Later he became head of the Stockbroker Network that was active around Belfort.
Rée argued that the Royal Air Force bombing of France was causing heavy civilian casualties and turning public opinion against the Allies. Rée had been impressed by the destruction of the locomotive works at Fives by Michael Trotobas. During the operation four million litres of oil were destroyed and twenty-two transformers damaged and the works were out of action for two months.
Rée suggested that the German war effort could be undermined more effectively by SOE agents organizing the sabotage of individual factories when when they were unoccupied. To illustrate his argument he arranged the destruction of the Peugeot factory at Sochaux.
The Germans became aware of his activities and attempted to arrest him. Despite being shot four times in the lung, arm, shoulder and side Rée managed to escape by swimming across a river and crawling four miles through a forest. Rée eventually got back to England via Switzerland.
After the war Rée was appointed headmaster of Watford Grammar School. He later became professor of education at York University (1961-74) where he became one of the country's leading advocates of comprehensive education and was active in the Society for the Promotion of Educational Reform.
I can't say it was simple patriotism that moved most of us - there was very little of that in the last war, it was much closer to simple impatience. You see, after the fall of France most of us in the army in this country had damn all to do. We were pushed off to Exeter or Wales or Scotland, nice safe places where there was very little to do, while wives and families were often in London or Coventry or Plymouth, all places which were being bombed - they were at risk, while we weren't. I think a lot of men resented this. And there was another thing; if we were going to get into a risky situation, we wanted to go somewhere where we would be our own masters. We didn't want a stupid colonel ordering us to advance into a screen of machine-gun bullets when we didn't agree with the order - we weren't the Light Brigade. If we were going to advance into a screen of machine-gun fire or do something equally suicidal, we wanted it to be our decision. That was something else we shared - and agreed about. But it made us all different. We were all individualists.
Ree now found that circumstances compelled him to invent an improvement in economical attack, a type of attack equally sparing of life that saved time, risk, and trouble as well. His first coup in this new style lacked the bravado of the Fives-Lille raid; but it was quite as cool, the initial risk for the principals was quite as great, and the results were a good deal better.
The Peugeot motor-car factory at Sochaux by Montbeliard had been converted to make tank turrets for the German army and Focke-Wulf engine parts for the German air force. To put it out of action would obviously help the allied effort. Though it was on bomber command's target list, it was a small target that would need to be hit precisely if it was to be usefully damaged at all; and it was sited close to the railway station in a populous part of the town, so that near misses on it would probably kill many Frenchmen - as indeed happened when the RAF made an ineffective night attack on it on 14 July. The mean point of impact of the bombs was nearly a kilometre from the factory, in which production was undisturbed; some hundreds of townspeople were killed. Ree knew already from local friends that some of the Peugeot family at least favoured the allies. Ree called on him, and suggested that the director might like to help sabotage his factory, instead of facing all the damage that would ensue when the RAF returned to do the job properly.
The unique form of sabotage took place in the Peugeot works at Sochaux near Montbeliard. A motorcar factory in peacetime, it was engaged in production for both the German Army and the German Air Force. The RAF chose it as a target for an attack on 14 July 1943. No bomb landed within a kilometre of the factory, but a number of French civilians were killed.
Ree, who was sitting under a peach-tree some miles away when the bombing took place, decided he must find a better way of putting the Peugeot factory out of action. He succeeded in contacting Robert Peugeot, whose pro-Allied sympathies were fairly well known, and suggested to him a pact whereby effective internal sabotage would be carried out against an assurance that the factory would not be attacked again from the air.
Peugeot naturally asked for evidence of Ree's good faith and of his power to guarantee immunity from bombing. Ree therefore asked him to choose his own code-phrase which the BBC would then transmit at a prearranged hour. When the BBC did so Peugeot decided to trust Ree and give him plans of the factory and the necessary inside contacts.
A team of saboteurs was assembled, for whom Ree arranged an escape route to Switzerland. While waiting outside the factory gate for someone to produce a key the saboteurs played a game of football against some uniformed German guards. When a home-made bakelite bomb fell out of a saboteur's pocket a German guard politely handed it back to him.
Extensive and carefully selected damage to the factory was caused. The RAF, which had initially accepted Ree's plan with reluctance, duly maintained the embargo on bombing, although SOE's suggestion that the Sochaux experiment might be repeated elsewhere did not meet with approval.