Simple, I think: instead of forbidding the use of chemical weapons, as he did historically, Hitler explicitly orders his military to use chemical weapons against the Allies as retribution for his experience in WW1.
That´s when the gloves really come off.
Yeah. The war in the Soviet Union bogs down as in OTL, so the Germans escalate to gas. The Germans don't give a shit about the Soviets, so they figure all options are on the table and they use them. The British start gassing German cities. The Russians gas the German army. The Germans respond by gassing London. The British escalate to anthrax and the Americans escalate to nukes.
Wow! That is a REALLY messy war.
Although he claimed that the work at this institute involved only 'defensive' measures against biological weapons, Heinrich Himmler, Herman Goering, and Erich Schumann, head of the Wehrmacht's Science Section, strongly supported the offensive use of chemical and biological weapons against Britain, the Soviet Union, and the United States.
According to Kliewe, plague, typhoid, cholera and anthrax were being developed as weapons, as well as a new "synthetic medium for the spread of these bacteria" which would allow them to remain virulent for eight-to-twelve weeks.
As part of the Nazi biological warfare program code-named 'Blitzableiter' (Lightning Rod), Blome's Institute was therefore "a camouflaged operation for the production of biological warfare agents", and its construction was overseen by Karl I. Gross, an S.S. officer and specialist in tropical diseases, who had conducted lethal experiments on 1,700 prisoners at the Mauthausen concentration camp.
http://en.wikipedia.org/wiki/Kurt_Blome
During the war, Germany stockpiled tabun, sarin, and soman but refrained from their use on the battlefield. In total, Germany produced about 78,000 tons of chemical weapons. By 1945 the nation produced about 12,000 tons of tabun and 1,000 pounds (450 kg) of sarin.
Delivery systems for the nerve agents included 105 mm and 150 mm artillery shells, a 250 kg bomb and a 150 mm rocket. Even when the Soviets neared Berlin, Adolf Hitler was against using tabun as the final trump card, a decision which stemmed from his own experience with chemical weapons in World War I.
http://en.wikipedia.org/wiki/Germany_and_weapons_of_mass_destruction
The French put up a better fight in 1940 ... the Germans have to fight for every inch of ground. As the campaign grinds on Hitler offers Franco vast areas of France in exchange for Spanish help and they attack the south of France also drawing them into the war on the Axis side ...
How about about a scenario where Germany retains just enough of its scientists to make an atom bomb by mid-april. Hitler fires at the USSR then kills himself. The blast destroys the Soviet government,plunging the nation into civil war.
I meant EVERYONE who could hold the reigns of power. No Beiria,no Zhukov,No one !
no atomic bomb on Japan. Total blockade of the islands drop chem/bio burn all crop fields, and sink all fishing vessels except no surrender starve the entire pop of Japan to death.
I don't know if WWII would necessarily be that much more brutal, but the changes at the end of it would definitely be a lot more revolutionary and irrevocable. There could be no more talk of any sort of return to status quo ante or Wilsonian international law if the British Expeditionary Force was cut off from the sea and surrendered. Not from Churchill and not from Roosevelt. The British Empire is from that point on kaput. Finished. Dead. As is the French and Dutch Empire. All arrangements are from that point on ad hoc.Franco I suspect would have joined the Axis had the BEF been far more damaged or Hitler went to Spain after the fall of France and offered him the kind of deal he couldn't refuse.
The BEF only getting a fraction of the number of men out they did OTL would present once of the biggest changes in the war. Lets say they get enough out it doesn't collapse Churchill's government, but lose enough that the British Empire has to pull heavily from its colonies to defend England. In that case I actually could see quite a few countries quickly toss in with the Axis like Spain, Yugoslavia, and even potentially Turkey heck potentally even Greece so they don't get carved up by Turkey, Yugoslavia and Italy. There would also be large uprisings many places in the British Empire. It would be quite ugly.