In this thread about the V1 (buzz bombs) and V2 attacks on London during WWII, there is a link that states that the V1 attacks commenced on June 12, 1944.
Is it strictly a coincidence that this occurred within a week of D-Day, or was it Hitler’s revenge for the invasion?
This page says
[Luftwaffe Colonel Max] Wachtel had been ordered to begin launching the pilotless bombs against England by June [1944], but his unit had no equipment, no launching rails and no supplies. It had been decided that lightweight launching ramps, called modified sites, would be used in place of larger ramps that had proved too vulnerable to Allied bombing attacks.
The supplies and equipment that Wachtel needed to begin operations did not arrive until June 12, 1944, only a few hours before he was to begin launching V-is against southern England. Only 10 ramps were ready for launching; 55 were supposed to have been prepared, but not enough spare parts and equipment had been sent for all of them.
By 3:30 am, on June 13, the 10 firing ramps were ready. The Luftwaffe high command decided to go ahead despite the fact that so few ramps were operational.
but on this page it says
Albert Speer in his book “Inside the Third Reich” claims that the V weapons (especially the V2) could have been working many months before June 1944 if the men at Peneemunde had been given more support from Berlin. Speer cited Goering as the man who had little faith in the project. Their impact, if used from an earlier date, might have been greater.
and this page says
But Hitler was more eager to hit London than to fight a defensive war [after the D-Day invasions]. He had a weapon to do it with, the V-1. It had first been flown successfully on Christmas Eve, 1943; by June 1944, it was almost ready to go to work…
On the afternoon of June 6, Hitler ordered the V-1 attacks on London to begin. As was so often the case, he was giving an order that could not be carried out. It took six days to bring the heavy steel catapult rigs from their camouflaged dumps to the Channel coast. The attack did not begin until June 12, and when it did it was a fiasco: of ten V-1s launched, four crashed at once, two vanished without a trace, one demolished a railway bridge in London, and three hit open fields.
It looks to me like D-Day definitely spurred the Nazis to commence V-1 attacks, but even without the Allied landings, it seems likely that there would have been V-1s hitting England sometime in the summer of 1944. On the other hand, it does seem possible that V weapons could have been launched even earlier than that if they had been given higher priority–if you can believe Speer.