In addition to Belthazar particule-centric breakdown, I think it’s also important to do a clause analysis when reading long sentences.
Basically read until the next verb to get a clause, then look just after it to determine what kind of clause.
Well, this one is an annoying exception, Japanese really like to put temporal adverb at the beginning of the sentence. It’s the same for topic marked with は. If we see a temporal adverb or a は, we can reset out internal parser. So let’s find the next verb + 1.
多く…出した太平洋戦争. The verb 出した is followed by a noun so we know that the clause [多く…出した] is just qualifying 太平洋戦争.
So everything before 太平洋戦争 is just some details about it. In English we can actually translate it as a nice little sentence. The pacific war claimed many victims.
Now we can reset our internal parser at 太平洋戦争 and parse until the next verb.
verbてから is a grammar point, and structurally it’s linking two clause clause1てからclause2. “clause1 and then clause2”
So clause1 is complete and the core is just noun1がnoun1をむかえる
noun1 welcomes noun2. The pacific war welcome the end. A bit clunky in English but understandable.
Then reset the parser after the てから and go to the next verb + 1.
The verb is followed by an ‘。’ so we hit the the end of the sentence and also the main clause, which is always at the end. The main clause is very simple, it’s a nounが経ちました. More than 70 years passed.
So in the you can read the sentence very neatly, from left to right and from clause to clause:
In 1945. The pacific war claimed many casualty. The pacific war welcomes the end. And then more than 70 years passed.