They were a hastily organized and marginally effective Nazi guerrilla warfare organization. While they weren't very effective, according to the liked book review, they did conduct sporatic attacks into 1946 or 1947.

"Clausewitzian partisans" are part of orthodox military doctrine. They are militia who operate behind the lines in territory occupied by the enemy. Their function is to cut supply lines and generally cause confusion, but their operation presupposes the continued existence of a national government and a conventional army. The Germans had experience fielding irregular forces of this nature, both against Napoleon and in the form of the independent "Freikorps" units that operated in eastern Germany during the chaotic period just after the First World War. The Germans started thinking about them again as soon as the situation on the Russian front began to deteriorate, and in fact anti-Communist partisans did the Red Army appreciable damage. It was only in the last half of 1944, however, that the Germans began to focus on the possibility that the Allies might have to be resisted within Germany itself.

This was a job that no major player in the German government or the military wanted to be associated with until the last moment. Thinking about the penetration of Germany, even the extended Germany of Hitler's annexations, implied a fair amount of defeatism. Additionally, the military was not keen on sharing its dwindling resources for training and material with civilian stay-behind groups. In principle, the Werwolf was commanded by SS Chief Heinrich Himmler, through a back channel consisting of local chiefs of police. These middle-aged men tended to regard partisan activity as somewhat disreputable, and in any case had no idea how to go about it. Far more dynamic, and only nominally under SS command, was the Werwolf program operated by the Hitler Youth. The story of the Werwolf proper, in fact, is largely a cautionary tale about what happens when you give teenagers a license to kill.

Despite all obstacles, training programs were improvised for youths and adults, though the courses sometimes lasted just days. Underground bunkers were prepared in isolated areas, from which the Werwolf were supposed to emerge to strike terror into the enemy. Werwolf was supposed to mesh into the larger project of establishing an "Alpine Redoubt," a base in Austria and mountainous southern Germany to which conventional forces might retreat. Certainly the major Werwolf training bases were located in that area. The last-minute attempt to build underground facilities in the Alps were too little, too late, and the armies ordered to go there never arrived, for the most part. In the final few days, Hitler decided to stay in Berlin, rather than go south and try to organize the Redoubt from Berchtesgaden. Still, it was not quite just a propaganda ploy.

What did the Werwolf do? They sniped. They mined roads. They poured sand into the gas tanks of jeeps. (Sugar was in short supply, no doubt.) They were especially feared for the "decapitation wires" they strung across roads. They poisoned food stocks and liquor. (The Russians had the biggest problem with this.) They committed arson, though perhaps less than they are credited with: every unexplained fire or explosion associated with a military installation tended to be blamed on the Werwolf. These activities slackened off within a few months of the capitulation on May 7, though incidents were reported as late as 1947.