Hi, currently reading about military intelligence history and i'm going through operation stella polaris which was an elaborate project to evacuate the whole of finnish military intelligence personnel to sweden when it became apparent that soviets wouldn't care to do fair court martials after the war.
One paragraph really caught my eye and i'm looking for more information. All i can see online is mere gossip or in swedish.
22.2.1944 5 bombers from a large soviet bomber squadron destined for turku - finland deviated from their bomber group and changed course to stockholm. Their course change was immediately picked by radio intelligence service several hours before the main bomber group was even close to turku.
Those 5 bombers flew to stocholm, dropped their bombs simultaneously to 5 targets (one being a barracks) and very soon soviets declared the bombings publicly as an navigation error.
However finnish military ingelligence later raported that such elaborately controlled "error" was impossible in clear sky daytime raid.
According to the publication, all this was escalated after sweden imprisoned Vasili Sidorenko as a spy in 1942 - which very soon resulted in Soviet Union banishing swedish ambassador and military attache.
Apparently Vasili Sidorenkos incarceration resulted in very strong public outcry from Soviet Union and Molotov himself. Soviet union also made a threat to bomb stockholm (this is what i'm interested about).
Sidorenko was freed 2 days after the bombing.
Funny thing is, finnish intelligence was aware of the planes heading and apparently relayed that information to swedish FRA, yet no AAA guns ever fired at these planes.
Most likely, this was an error in navigation and nothing more.
The bureaucratic process to free Sidorenko was started over a month before the bombings and was initiated due to Soviet pressure.
The Soviet long-range bomber force was notorious for its inablity to navigate in darkness - the Finns repeatedly managed to fool the Soviets with bonfires on the ice outside Helsingfors, making the Soviets drop their bombs on the ice instead of the city.
220 bombers started for the raid against Åbo/Turku, and only about 100 actually found the city - and only a handful of bombs actually hit Åbo/Turku. The rest milled about southwestern Finland, dropped their bombs all over the countryside, and a few flew in over Sweden.
The Soviets also bombed Åland that night, and managed to hit the electricity plant in Mariehamn, which made all of Åland go black - all the lights that could be seen for the Soviet air crews coming after that first group was the ones in Stockholm and Strängnäs.
There is bound to have been dozens of planes deviating from their course for the Finns to note. Also note that they attacked both Stockholm and Strängnäs, two cities 60 km apart - so the Soviets were hardly maintaining formation.
The bombs were dropped around 21:00 on the 22nd of February and 03:00 on the 23rd of February - while the Soviets might have have started and perhaps also for a short while have been over Finland in daylight, by the time they were crossing over to Sweden, it would have been pitch black. The sun sets 17:00 in Stockholm on the 22nd of February.
The peacetime barracks of the armoured regiment P3 in Strängnäs was hit by a single bomb. In Stockholm, an outdoor theater was hit, as well as a civilian car workshop - all on Södermalm. Most bombs seem to have been dropped on the alotment outdoor/park area at Eriksdalslunden. And those were bombs that hit something. At least 20 bombs were dropped on islands in the archipelago.
The Swedish AA batteries did catch several planes with searchlights, but were not given permission to open fire. According to one second-hand source (an eyewitness account) they did fire and shoot down one Soviet bomber, but I have not been able to verify this.
The Soviets initially claimed that the bombings must have been done by German and Finnish planes attempting to provoke Sweden into a war with the Soviets, only later, when faced with evidence, did they claim error in navigation. If they actually wanted to show Sweden that they had the capacity to bomb Stockholm, they would most likely claim error in navigation from the start.
To summarize:
The attack was a night-time attack.
The Soviet long-range bomber force was notoriously bad at navigating at night.
The bombs fell with 6 hours apart.
The bombs did not hit even close to anything vital.
The bombs hit an area about 100x100km.
Sources:
Havsbandslinjen i Sthms skärgård 1933-45 by Urban Sobeus.
Hemligt krig by Jukka L Mäkelä (Swedish translation, 2nd hand)