it wasnt effective; it is b etter for Allience to built landing ships and airplanes-and Army too.
As it was it failed to bring about an immediate surrender and arguably was merely stiffened the resolve to fight on. More selective bombing to knock out dockyards, shipbuilding, aircraft factories, railways and other econopmic targets would have had a better effect but had some of the resources been directed against U-boats the wear might have ended earlier. The official naval historian Stephen Roskill estimates that more resources to coastal command could have taken 6 months off the war.
Interesting.Hipper's Battlecruisers killed civilians when the shelled the Easdt Coat Towns in 1914, they didn't restrict their bombardment to harbours.
The way I understood it, the strategic bombing campaign contributed a great deal to winning the war, tying up a huge proportion of German industrial capacity in air defence production and helping the war on the Eastern Front a great deal.
Personally I think that an increase in massed strategic bombing over Germany would not have had any significant impact - except possibly in the post-war years where this sort of action would be seen to be even more reprehensible & morally dubious than it was in OTL.
Just like it tied up a huge proportion of British industrial capacity and 1st rate manpower!
Furthermore the number of heavy bombers Costal Command needed to secure the SLOCs was minimal compared to the demands of bomber Command. And last but not least let´s not forget the one thing you need to fight a battle are secure lines of communication. So: subs first, cities second.