[Major battles or skirmishes/individual firefights within overarching conflicts? 53 major battles is more than enough for an entire war, but accomplishing 53 strategic goals over a year split between the two factions, or 53 minor conflicts within an important battle seems reasonable. What's the timeframe, anyway?]
Eric left the cursed dining hall, now effectively walled in, and made his way back to the panic bunker, relieving Cog and the mining team from defense duty. It was time to let everyone out so they could get back to work. Especially on that damn curtain wall. Even without a primary keep prepared to house artillary and anti-air defenses, they need some defenses. The first couple meters of wall at head height serves as a minor obstacle and good fortification for marksdwarves, but by the time it's the full 3-5 stories tall it will provide excellent defense from ground troops and effective fortifications. Once the tower was complete, it would be a real chore for any army to break through. An attacker would never gain enough wealth, political prestige, or strategic advantage from the destruction of the fortress to compensate for the sacrifices such a siege would demand. Only the goblins would bother, and only to appease Armok.
They needed special plans for the dragons, if they ever showed their ugly mugs again. They defied all rules of conventional dwarven warfare, more akin to the digital age of warfare he'd grown up with. With air strike capabilities and nearly half of their number being large enough that they could simply bound over the walls even if flightless, the fortifications would be useless. Their breath attacks and the fact that some unknown fraction would likely have magical potential meant that siege engine crews wouldn't be safe no matter how small the openings for their weapons were, as a dragon could easily latch onto the walls and breath right through, torching or freezing them with minimal effort and only the risk of the first dragon to attempt an attack on each crew being impaled by a pre-loaded bolt. Even with the advantage of the great range of the ballistae and legendary warriors of every variety, a single battalion of dragons could overrun the entire fortress and have just enough number remaining to occupy it until reinforcements arrived. No matter what, it was a losing battle. Actual firearms would be necessary, but they couldn't even produce enough suitable explosives to assist in mining operations, let alone operate enough .50 caliber machineguns to stop a flight of dragons short of the curtain walls. It would end up looking like ground crews trying to stop a bomber raid in WWII.
Steam-operated ballistae and crossbows? Or designing better rockets... The ostrich egg bombs and rocket barrages had worked wonders on every sieging force the old fortress had encountered. They could be adapted to shoot down airborne threats with relative accuracy, or deal heavy damage to larger units before they could close.
Nononono, I've got this! Magma rail guns! The explosive force of the pressurized magma deep below the fortress was great enough to lob small projectiles thousands of feet straight into the air from a "barrel" that didn't offer any extra pressure. If they used that power to lob a projectile from an actual rifled barrel, it would effectively let them constuct cannon turrets operating off pipes connected to a pressurizing chamber deep below ground, if the magma reservoir was great enough for the task. The turret could possibly be completely sealed off besides the barrel, protecting the crew and part of the equipment. Using adamantine plating and barrels, the turrets would be nigh-invulnerable to absolutely everything, including anything the dragons could wield, and require little material to construct, although no adamantine had been extracted so far. There were some deposits available, though, and they could technically spread out underground as much as needed to collect more.