What were the odds of surviving as a soldier from the beginning to end of WW1 / WW2?

In WWII, your odds of surviving depended very much on your role, your nationality (hence, equipment), and where you were on the line. For instance, in France, the British faced the bulk of the German armour near Falaise, compared to the Americans on their flank; as such, according to Max Hastings, the British lost a third of their continental armour attacking Falaise (which would subsequently be replaced).

Your odds of surviving D-Day depended upon where you were deployed: British/Canadian landing beach - Gold, Juno, Sword? Good odds. British gliders at Pegasus bridge? Good odds. (D Company of Ox and Bucks lost two casualties on the day) American at Omaha? Heaviest casualties of the day - 800 out of a total of 3,000. Airborne at Sainte-Mere-Eglise? Heavy casualties likewise.

D-Day was not the end of the battle, but the beginning. By July of the next year, the Allies had sustained 120,000 casualties across France, from Caen to Falaise, which is obviously far more than the 3-4,000 who died on the day. D Company, for instance, lost two men KIA on the day itself, but sixty in a skirmish on a later day.

As for role, rifleman was the most deadly. The rest varied by theatre - in Europe, a tank crew member was more likely to be killed than someone in the artillery corps, whereas pilots and sailors were at more risk in the Pacific simply because they were more common than tank crews - and by time period (obviously, you didn't want to be in the Japanese navy in 1944, because you were more likely to die than if you were in the Japanese navy in 1942).

The short of it is this: in all nations, the odds were bad if you were in the army, better if you were in the navy (in some nations, this included the air force, like Japan's carrier-based force; in other nations, like Germany, the air force was its own beast, and had worse odds than the navy.) If you were in the army, the closer you were to the front (rifleman, tank), the more likely you are to die.

By theatre, being German on any front was not good, but being German or Soviet on the Eastern Front was particularly not good. Being Japanese was marginally better, but not by much. If you were from the Commonwealth or the US, your odds were a whole lot better (the US style of combat has been described by I believe Geoffrey Regan as "a maximum of firepower and a minimum of finesse").

If you want to know the odds of a specific battle, it's a matter of looking at total forces committed, total casualties, and figuring the percentage, and then remembering that there would be support personnel (less likely to be killed) and those on the frontline (disproportionately likely to be killed).

I couldn't break it down specifically to look at the odds from start to finish, though, but rather the odds from end to end as a whole. That opens up to a whole bunch of other factors - for instance, is a veteran more likely to die because he sees more action than someone conscripted in 1944, or is he less likely to die because he's been hardened by battle and has more experience with what to do than the conscript? And then you have to factor in changing circumstances (more efficient means of killing, change in air dominance, etc). That makes it more prickly.

Would have been a bit better to be an American sailor than a German rifleman.