Battlefields have changed A LOT over the ages. Take the last 5 big wars my country has fought in.
1870 in the war between France and what would become after the german Kaiserreich, they fought a series of battles and within a month the French Emperor was captured and it was mostly over. Here you have cannons and rifles and such and also cavallery, but mobilisation(number of troops and equipment) and communication/transportation-technology do not allow for a true "front line", rather you have armies that engage in single battles that are decided within hours or days, this is the way wars were fought in the centuries before (f.e. the Napoleonic Wars and the American Civil War were fought in a somewhat similar way )
Fastforward to 1914 and WW1
The start of the war is pretty similar in the east vs Russia, but after a few month the western front gets stuck. Thats because higher amounts of troops that can shift their location via train and cars etc, now allows for a continous frontline between France/UK and Germany. Now the porcwar begins(think 16v16 on fields of isis with both sides heavily entrenched, but without any heavy units or superweapons, though lots and lots of berthas and cerberus and tremor) and lasts for about 3 and a half years when attrition, hunger and the spanish flu force germany to surrender(the troops still stood in french territory).
Personally I think WW1 was the worst one if you consider the perspective of a soldier. Weeks and months spent in trenches, constant artillery (2/3 of casualties if I remember correctly), often not enough clean water, first use of things like chlorine gas (also the first tanks and airplanes and submarines, though they were not really relevant in this war). And after the artillery, you have to storm the other sides trenches. My history teacher told us they calculated you'd need 3 to 1 ratio of soldiers to attack, first one dies/get wounded on the way to enemy trenches, second one in the enemy trench, third one kills enemy soldier either with the gun or the bayonette (swordblade attached to the gun).
If youve ever had the notion of serving in the military/in a war, listen to this first:
All in all this was the first fully industrial war.
If you really want to know about life as a soldier in WW1 I recommend watching the 1930 version of ALL QUIET ON THE WESTERN FRONT, its an american film but its based on a book written by a german soldier who fought in the war.
Fast forward to 1939 and WW2
Even though its just 21 years since the end of WW1 industrialisation has fully matured. Now tanks, airplanes, submarines, and for the pacific aircraft carriers, play a large role.
The French thought this war would be fought like WW1, which is why they built the Maginot Line, a series of useless but stong defensive positions along the french-german border. Useless because tanks (and supporting logistics) have become much stronger and so the german troops just blitz through the plains of NE and BEL and rush to Paris.
WW2 has endless scenarios for soldiers. You get your dogfights of planes and sea warfare in the pacific between US and Japan, and after the french surrender there is the battle of Britain (dogfight and bombing), later the same over germany (my city was hit by 400k firebombs within one night, 10%killed same heavily wounded, 80% of houses completly destroyed), and in the atlantik is submarine-warfare by the germans vs the british and american navy and support lines).
On the eastern Front you get lots of battles, but also sieges/semi-sieges, particulary in Lenin- and Stalingrad (St.Pertersburg and Wolgograd). The winter war comes to mind here, German tanks got stuck because the fuel froze solid... so think about what that meant for ordinary soldiers on both sides.
And all that ofc ist just part of the battlefields (the Chinese fought against Japanese invasion and amongst themselves since years before+African Campaign+attrocities in the Balkans and Greece etc.)
And most importanly, what sets it apart from many(but not all)other wars and power struggles, is that it explicitly was fought to eradicate a people. So you ask was what WW battlefield can look like and one answer could simply be the rounding up and executing of civilians in various ways.
If you want to know about the soldiers perspective of WW2 as for movies I'd recommend The Bridge, The Boat or Saving Private Ryan, those are mostly Anti-War movies, that get close enough to the truth(as opposed to alot of American war movies that are rife with patriotism and serve as warglorifying propaganda). Ofc there are loads of documentries out there.
As for the Holocaust and other atrocities on civilians, Id argue movie wise Schindlers List is the best starting point and then are many ways to continue, you could go to
https://www.yadvashem.org/ or ask Bhaktivedanta(I know he just watched and read stuff about the Nuremberg trials/the aftermath of WW2) or me about it.
Flash forward...
Not so much.
1945 WW2 in the pacific ends with the first, and till today only, 2 Nukes ever used against humans on Hiroshima and Nagasaki.
Those bombs killed about 150k-200k humans, half instantly, half after severe and sometimes long injuries. And the destroyed about 12-15 squaremiles on the ground at a strength of about 16 kilotonnes which is about 10-20 times stronger then the explosion in Beirut last year(easily found on yt). But a few years later they invent hydrogenbombs which can be more then a 1000 times stronger and you get this
So from 1945-1990(but really until today and a possible US-CHINA rivalry would be similar in some aspects),
you get the cold war aka. WW3
Direct war between superpowers now becomes impossible, because you have the military doctrine of MAD(mutually assured destruction). Battlefields consist mostly of watching/guarding/building, I live less the 50 km from the old GER/GER border which consiteted of armed guards and a huge minefield that ran for hundreds of km from north to south straight through the country plus radar, plus nuke stations plus AA etc.. For Americans/Russians/British think about bomber crew or guys that operate nuke or AA silos or submarines.
Plus you get the proxy wars, here the fighting continues somewhat similar to WW2, but altered by different terrain (think Vietnam or Afghanistan) plus more and more the fighting is asymetric, meaning you have a nominally stronger side while the other superpower only indirectly supports the "rebels" (f.e. US vs Vietcong; Russians vs Mudjahedin; US vs Taliban etc.). Also in this time you get political meddling on a smaller military scale, think special ops assasinations and/or coups, especialy in Latinamerica.
And for the last ten year, military warfare has shifted to include hacking, in 2010 the USA launched Stuxnet to destroy Iranian nuclear centrifuges and since then the military/political use of hacking and/or trollfactories to influence solcial media has only intensified, so if you ask what WW4 battlefield looks like I'd say its sometimes pretty similar to us, aka a bunch of guys in front of keyboards, only they arent playing for fun.
As you can see, if you get me in teacher mode Im always willing to talk :-), so if you want to know any specifics just ask away.
