In third person limited or omniscient narratives Readers tend to have better information (perhaps even close to perfect information) than the characters in the story just by dint of being the reader, and being removed from the situation. This is especially true in a story with multiple perspectives. A reader can see multiple characters and locations across a story, and unless ample care is taken to show them otherwise (care that can be viewed as paternalistic or repetitive) they can be lost to the conclusion that the characters can accrue such information.
To a reader, characters often look "stupid" or "incompetent" by committing mistakes due to imperfect information. A simple example is the obvious villain in a movie. We see a man who looks really sketchy and we judge him hard -- from our distance he's definitely the villain. He will definitely betray the protagonists, who were idiots for ever trusting a man with a handlebar mustache and skull-print pajamas. We throw our hands up in the air in frustration. This is an extreme example, and there are certainly ways to avoid it, but overall, it's easy for a reader or viewer or otherwise a consumer of media to lean on their perfect information.
This presents a problem in war stories because most battles are won on a balance of information and lost to what seem like careless mistakes, with enough distance from the events. Nowadays an imperialistic industrial country can zoom its satellites down into the enemy general's toilet if they wanted to, but before Operation Barbarossa Nazi Germany had to risk flying spy planes as far as they could around the Soviet Union and taking altitude photographs to begin planning their attacks.
A bunch of those photos were grainy and wrong and misinterpreted and continued to be used months after they were utterly obsolete and even while people involved on the ground KNEW the photos were wrong for the simple fact that they were walking around the same photographed area and knew the high command had gotten something wrong. That wasn't a military base, it was an obsolete tractor factory. Oh well.
But it was the best information they had at the time; in some cases the only information they had at the time. You need information that your troops can digest. Sometimes it's really terrible, and you make do.
Fog of war isn't just a concept in video games. It's a term of military planning and strategy, and it symbolizes the distance between high command and ground command, between ground command and assets, between assets and their environment, and even between political command and high command; and then, between all of these and their enemy counterparts. For an operation to be carried out perfectly each element has to have perfect information not only on every other element, kept up to the minute, but also on the enemy as well.
This ideal is impossible, not just for real militaries, but for authors and for readers. You cannot write stories about this or in this fashion or else there's no conflict, no back-and-forth, no reverses. Two equally equipped, perfectly informed enemies will arrange themselves in opposing lines and not fight. There has to be a deficiency somewhere.
Military command is a game of telephone that begins with the actual, platonic ideal of the information of what is happening, and is quickly filtered through erroneous perceptions. At the high command level you're expected to have some idea of the enemy's intent and capabilities; on the ground level you're expected to have some idea of your environment, its dimensions, and the way the enemy can or is using it. Most times you don't. Snipers are a perfect example. They exist to take advantage of the fact that you won't know where they are.
Every time a sniper kills someone, there is the potential for the reader to think that person is an idiot. That's an extreme way of looking at things but it illustrates the problem. A story character can't read the tense prose or listen to the ominous-sounding music and look around the empty foreground and go "yeah this is the sniper scene i better be careful."
It's hard to properly convey to a reader these facts without sounding like you're an idiot or that you think the reader is an idiot. But the characters in a story must necessarily operate on imperfect information, they must be flawed or make mistakes, or else there can't even really be a story to begin with. There's very little conflict to be had otherwise and in my opinion it would feel really unrealistic and expedient.
You can't really ask people to be charitable. And there are some mistakes that are egregious -- if a character makes the exact same mistake a lot of the time, then it had better be a tragic shortcoming, or else (and probably even still then) the reader will just think they're hopelessly stupid. But regardless of all that the truth is still that not every conflict can be resolved by sheer skill or mismatch of skill. Most conflicts are in fact won by emotional impediments, informational shortcomings, and just plain mistakes that don't look like mistakes at the time to the characters, but may look like obvious mistakes to the reader.
You can try to mitigate this by setting up the personalities involved carefully. Have characters second-guess themselves; have characters who receive information that the reader believes is true as well but swing it around and make it wrong; have characters who disregard correct information but make sure they provide good reasons for doing so, that feel like they come from an intrinsic part of the character. It feels like a cheap reverse at first, probably, but it sets up the fact that people on the ground, and by extension the reader, don't have all the answers. You have to slowly get the reader to think in-universe, and to see that your story is operating on perspectives that aren't always true.
You'll always get a couple of people who'll take a weird tv tropes attitude to things and take all information in the story as either perfect or contradictory, looking at it from the outside-in. But hopefully over time you'll get most people to respond charitably to the fog of war.