I will take your last sentence to reference the American Civil War and make a small tweak. More than giving battle during a forest fire you can find examples of the fire power initiating the forest fires that played a role in the battle.

Black powder used in most of the 19th century as well as the explosives of the time were more prone to start a fire than modern ordnance. There are testimonies of artillery fire starting forest fires in May 1864 during the Battle of the Wilderness in the Eastern Theater of the American Civil War. As you can expect fires hindered maneuvering and visibility.

The worst part seems to have been for the wounded, in the ACW many would lay in the field until the battle was over, sometimes for days, and casualties could be removed from the field. Civil War wounds have a reputation for being very nasty due to the use of big caliber rifles (.58 or 14.7 mm) that tended to expand open once they hit a bone causing very nasty wounds. Same for artillery shells, solid shots that cut limbs, canister which was a kind of huge shotgun etc.

Not trying to be gore just making the point that a wounded soldier was likely to be unable to move by himself lying where he fell until help arrived. It means that fires apparently engulfed a number of the wounded according to biographies and letters.

I'm sure that there are several cases of fires being caused by ordnance. The one that springs to my mind is the fires caused by the LCT launched rockets on the bluffs overlooking Omaha beach on D-Day.

The bombardment plan for Omaha largely failed. Cloud cover prevented the air force from bombing accurately. The time allotted for ship bombardment was too short for the big guns to achieve much.

Also there were nine LCT(R), Landing Craft Tank (Rocket), each equipped with around 1,000 3" rockets scheduled to fire on the German positions at 06:00. The rockets were aimed by pointing the entire ship at the target. Obviously the motion of the sea had a large detrimental effect on the accuracy of these rockets and they failed to hit anything significant. They did however start numerous fires in the brush on the bluffs.

Because of the wind blowing from the West the smoke from the fires drifted East across the bluffs and the German positions. The smoke did interfere with German vision somewhat. At the Eastern end of the Beach the smoke was quite dense. The Western end was quite clear though and units landing here (e.g A Company 116 Infantry Regiment) took very heavy casualties.

You can see the drifting smoke in pictures of the beach taken from offshore that day.