More people died in WII than in WWI, but not every combatant nation of WWII suffered worse (or even as badly) as they had in WWI.
The UK was the first in and last out of WWII, the only nation at war continuously the whole world war.
It was a far more deadly war and lasted for the UK, six years rather than four.
Its population during the last war was slightly larger than it was in WWI.
Yet, surprisingly, only about one third as many people died.
Dividing the total number of deaths (divided by the total number of war years) into the total wartime population , I get a figure for what I call the intensity of war deaths, one that is about one fifth as great for WWII as it was for WWI.
(Producing the percentage of total population who died in the war each year ---- admitably a very crude indice ---indicating one person in 200 died each year of WWI, versus one person in 1000 died per year in WWII.)
Put another way, in WWI the UK experienced a lot more total deaths over a slightly smaller population over only two thirds as many years of war.
Put yet another way, I am saying that 60,000 deaths spread over 10 years of war in a population of 250 million people (USA/Vietnam War) feels much less bad than to have a population of 2.5 million experience 800 deaths over a one week period (Israeli Jews/Six Day War).
The number of dead the UK experienced in head to head clashes between the Germany Army and the British Army in North West Europe for one month in 1940 and again for 11 months in 1944-1945, was very tiny set against the total of people dead as result of WWII.
Yet in a way, it was the key death-toll event of the entire war.
Because defeating the German Army upon German soil was the only way to end WWII quickly and at a minimum loss of life upon all sides.
It took six years for the UK to do to the German Army what it should have done in six weeks in 1939.
With Germany out of the war in 1939, Italy and Japan would never have gone on their quests for world wide conquest.
The French and British empires in combination in 1939 had a far far far far larger manpower pool to draw upon that the Germans so any land army war would have gone to the Allies in the end.
But a vast conscripted infantry/artillery-based army of British and Dominion working class enlisted men, in combination with millions of conscripted darkie soldiers from the colonies, all demanding benefits for having saved the Empire, was totally unacceptable to the British elite.
They wanted a war won by a few big very expensive machines, driven by a few well educated middle class very white British men : bombers, battleships and tanks.
In the event, they got their 'middle class war' and lost the support of their Dominions and Colonies in the process : hoisted on their own high tech petards in the end......