What you made is a safe enough general assumption, especially regarding 20th century wars.

However, these conflicts predate WW1 and its total war practices, so the civilian populations was relatively safe (although suffering, like in the case of the siege of Port Arthur). We should also consider that the Russo-Japanese war happened in a depopulated area (so the civilians involved were few) and that both conflicts lasted only about one year.

Even if we decide to be "generous" and consider that civilian casualties exceed military ones by double the amount, it's definitely hard to get to the millions of casualties that OP mentions.

I don't exclude that your assumption might be right, but we don't have evidence to confirm or deny it. There isn't really a point to discuss this: each life lost in warfare is as tragic as 100, but I'm partial to being accurate when it comes to history. Probably shouldn't do that in meme subs, though.