How effective were commando raids/operations during ww2?

Most of them failed, although Mussolini was liberated by a daring German commando.

Some attacks were not particulalry effective from a military perspective but had a lot of value as propaganda. There were several operations that could be argued to have had major impact on the outcome of the war.

Operation claymore for example resulted in the destuction of some fishing equipment, onthe face of it not too impressive. They did however get that hands on a set of wheels for an enigma machine and some codebooks which made tracking uboat movements possible and therefore allowing for convoys to avoid them.

There was also the raid that destroyed the heavy water facilities in Norway slowing down Germany’s development of nuclear weapons.

It could also be argued that all the training came in useful when it came to planning D-day.

US Navy Underwater Demolition Teams (UDTs) were effective, mapping routes and destroying obstacles in preparation for amphibious assaults. Amazing work, swimming right right up to heavily fortified beaches.
http://www.navysealmuseum.com/heritage/historyWW2.php

Norwegian commandos put a dent in German nuclear projects by destroying heavy water facilities and sinking a ferry carrying heavy water.
http://en.wikipedia.org/wiki/Norwegian_heavy_water_sabotage

The one that stole the Enigma code machine was successful. Otto Skorzeny broke Mussolini out of prison. A raid on Calais convinced Hitler that the Aliied invasion was going to occur there.

Not to mention all of the “Little” operations carried out by the French, Polish, and Finish Resistance Groups

Commando raids were usually planned to achieve a very limited objective. Capturing equipment, knocking out a key defensive position, killing an enemy commander, sinking a troublesome battleship, etc. They seldom had a strategic objective. Only two I recall were incorporated into a basic strategy: General Hutier’s “Sturmtruppen” on the Western Front 1917–18 and Skorzeny’s commandos grabbing key points in the “Battle of the Bulge” 1944.

@boffin The Finns in 1939–40 were magnificent. Stopped a Soviet force 100 times their size dead in their tracks long enough for the diplomats to convince Stalin it was useless. According to Kruschev, the USSR captured only “enough territory to bury our dead”.

was the enigma capture was a piece of good fortune or a planned objective?

@mammal It was a bit of both. A wrecked Enigma machine fell into the hands of the Polish resistance and it took a British SAS operation to get it out. Intelligence about the A4 rocket was also gathered the same way.