Attack of Smaug

The Conflict

Prelude

At first, Sauron's forces are weak and scattered. He also would not have the One Ring. Until he has a much stronger army and regained possession of the One Ring, he is vulnerable and cannot expect a victory. So he would have two major goals. First, rearm massively. The second is find the One Ring.
To do this, I think he would start with a move similar to what he does in the books and movies. Him operating openly from Mordor would pretty directly announce his intentions. But him operating in secret from Dol Guldur does not. So, setting up base there and beginning to rebuild some forces there is a good idea.
The next would be to deploy the Ring Wraiths to strategic points in order to conduct a series of related tasks. The first and most obvious would be look for the One Ring. The next would be to fortify their bases of operations and lead a local rearmament program. Next, they are to attempt to look for any more dragons (of any type or power level) or balrogs.
Related to this is disinformation. Should anyone start to get too inquisitive about what is going on in an area, the local Wraith is to spread false reports that some of those balrogs and dragons have been found or recruited. Ideally, the rumors are to involve geographic isolation from where any tangible leads on those are actually to be found. Lastly, proxy attacks are to be used to force the Free People on the defensive so they are not able to unite and attack.
So, where would these wraiths be deployed? Well, one would need to shore up support in Mordor's proxies and allies. This means one wraith for Umbar, the Easterlings and Southrons. Not Isengard as Saruman has not fallen yet. Then, two would need to be stationed in Minas Morgul and the Black Gate to search the most obvious attack vectors for those trying to destroy the One Ring. Then there is Angmar, Moria and Mt. Gundabad. All of those have major orc populations, little oversight by the Free People, are close to known dragon and/or balrog locations and also provide solid bases for searches. The last one would likely be sent to simply search the areas west of the Misty Mountains - possibly to recruit the trolls there. Or he might be sent to the Grey Mountains to attempt to get the aid of the dragons.
But Gandalf would not be static either. He too would be seeking the One Ring - but to destroy it. He would also be looking to gain any information on the activities and locations of Sauron's forces. His personal power base appears to be between the Misty Mountains and the borderlands of the Shire. Where the Rangers of the North and more "adventuresome" hobbits live. He would probably begin escalating his own operations when he hears of suspicious reports due to Ring Wraith activities.
Calling on his connections with Rivendell, Gandalf would probably get financial assistance to hire some dwarves to rebuild and garrison Weathertop. The elves would also probably provide specialist military trainers and advisers to this base. Once built and staffed, it would provide an intelligence gathering headquarters and informal training ground/armory. The goal would be to increase the ranks of the Rangers and provide them with better weapons. They would be asked to conduct aggressive raids and patrols to counter orc activities while monitoring reports to see where they are coming from. Ideally, this would provide them with trend lines to figure out where problem areas are. Meanwhile Gandalf would be quietly recruiting and training hobbits to aid in intelligence work and assassinations - the sort of dirty tricks I talk about them being suited for.

Deployment

Due to the power of dragons, it makes sense that the "loose wraith" is sent to the Grey Mountains and makes contact with the dragons. This is where Smaug's attack would come in. The orcs in the area that would come in later are a bit harder to get an estimate on. But this army would primarily be coming from the Grey Mountains instead of the Misty Mountains. Since the Grey Mountains appear to have lower concentrations of orcs, I suspect lower numbers available. Combine this with this taking place much earlier and the lack of reinforcements from the Misty Mountains and orc numbers would probably be lower. The movie version of the Battle of Five Armies had 10,000 orcs from Mt. Gundabad. The lower estimate for the book version is also 10,000. So I will say 10,000 orcs will be there to support Smaug.
On the defense, we will be starting off with just the dwarves and local Dale Militia. Because this is where Dale gets destroyed, it would be much bigger than Lake-town in the Hobbit. Probably closer to the version we see later. Which means I will estimate their militia size as 50,000. The Lonely Mountain would be in a similar position. At its height, it had 60,000 residents. During a crisis, between 30% and 50% would be under arms. But I suspect that the 30% would be closer to what is "standing". So at the very start, there would be 18,000 dwarves, which would rise to 30,000 after Smaug shows up.

The Engagement

So, I suspect that the attack on the Lonely Mountain would take place now. The idea is that Mordor would need to knock out such a major player. Its economic power and aid to Gondor would mean that without it, Gondor would fall much easier. Possibly under the weight of its own domestic problems. Yet it can't directly attack yet. So contacts with the dragons of the Grey Mountains would need to be exploited.
Smaug's attack would likely end with massive losses to the city of Dale. Essentially, Smaug would fly overhead beyond the range of the normal bows of the town militia. Said militia would naturally throw everything into the battle to save their homes. But they would know that the dragon would be too much for them. A general evacuation would be called and everyone would retreat to the Lonely Mountain. The dwarves would offer refuge to them, so some would survive.
But not all - the initial blitz that wipes out most of the city would be quick and Smaug would easily notice that there were large numbers of people fleeing. This mass would likely disorganized, easily spotted, poorly protected and flowing in the same general direction. Smaug would naturally target them next. Only the leading elements and those isolated people able to quickly hide would survive.
The city would probably be totally ruined outside of a few refugees. So that larger force would be virtually a non issue. Instead, I will say that the official numbers would be held. This means 2,000 refugees, 1,000 militia and 300 dedicated bowmen.
But due to dwarven experience fighting dragons earlier, it would likely result in the death of Smaug prior to the total destruction of the Lonely Mountain. But this is not to say that this would not be an impressive battle. First, Dale would be totally exposed and thus relatively easily destroyed in a surprise attack. Then, there would be the fact that the Wraith sent to recruit the dragons would not want a defeat. So, the surprise attack of Smaug would essentially put the Lonely Mountain under siege. Smaug - who is likely not old enough to be at full power, can't directly attack. The dwarves would not be stupid enough to attack a dragon in the open. Thus a stalemate would break out.
The wraith sent to the Grey Mountains would then respond by deploying an army of his orcs to aid Smaug. This army would be placed under Smaug's command, as the wraith can't expose itself yet. The eagles could not accept a dragon and orcs encroaching on their territory. Any survivors of Dale would see defeating this army as literally a battle for life and death. Elves would, like the canon version, send their forces. Both men and elves would want compensation for this destruction, seen as being invited by the greed of dwarves.
Then, we get to see the full power of dragons - their aerial fighting with eagles, ground attack powers against the men and elves, command of armies with the orcs. We can even see the use of the hypnotics as he tries to mind control his way into the Lonely Mountain or enemy commanders. With the battle raging outside, Smaug might make one last attempt to storm the Mountain and manipulate his way past the defenses.
But this would be the perfect chance for the hidden defenses the dwarves added after the War of Dwarves and Dragons. It is likely that Smaug would go straight for the defenses able to kill him first and attack them as brutally as needed. So they would need to be hidden until it is clear they would be able to deliver the killing blow. Which means waiting until Smaug is exceptionally close, with overwhelming force then applied.
So - what would this look like? The first thing of note is Smaug's main advantage is actually that he can fly. So something needs to negate that advantage. Smaug may be small for a dragon, but is still huge. So maneuverability is going to be an issue. Forcing it close to the ground in tight areas, such as near the main gate would be most helpful. Here, he would be between two mountain ridges that the dwarves would be able to prepare in advance.
Second, one would need a weapon that could realistically be expected to pierce the scales. Like a ballistae. Several of these on both sides would allow the defenders to hit Smaug from several directions at the same time, so any loss of a single one would not be crippling. Nor could a single fire blast knock them all out. As Smaug attempts to deal with those on one side, he would be hit by those from the other. This would create a situation where survival requires retreat.
Now, these multiple ballastae from hidden positions able to attack from several different directions is key. It is unlikely that a single shot would be able to kill Smaug. Yes, that is how Bard was able to kill Smaug with a normal bow. But apparently cow skulls are thick enough to cause an ill placed bullet to ricochet off. Hunters with 60 pound bows appear to aim to wound deer enough that they run off and die from bleeding because an instantly lethal shot is difficult. Possible yes, but hard. It is far more likely that the shots would just make him angry and angry dragons go on the offensive.
So instead of the kill shot, the ballastae should essentially have whale harpoons on them. The bolt should aim to shoot through the wing. Then, the head needs to be set up so that the harpoon gets stuck. Perhaps a pressure activated spring like thing that opens up hooks. Then, the rope attached to it can be reeled in so that it pulls Smaug out of the air. Should several of these embed themselves, Smaug can be effectively immobilized. Then one can try and hit vital organs.
Or the commanders can send the ground troops in. Such an option would need to be prepared for in case Smaug breaks free from the harpoons holding it down. Should this happen, the ballastae would be much more vulnerable to attack and it would be harder to aim the kill shot. But, the need to get to a high point and/or use strong winds means that Smaug us essentially still grounded. Which means more nimble troops would be useful.
These troops would need to get in close in order to be effective. Specifically so close to the torso that Smaug would struggle to use his tail, teeth, fire and claws to his advantage. The main target would likely be the Caudofemoralis Longus muscle, which attaches half of the tail to the back legs on large dinosaurs. This muscle helps walk, maintain stance and bear the massive weight the dragon would be carrying. So striking here would cripple it. Then pikes could be used to aim at the vital organs.
We have to remember that the dwarves are able to make armor able to withstand the heat of dragon fire. So odds are the front line defenders would be completely covered in first rate armor built for this purpose. The need for massive damage to be done as quickly as possible would require heavy weapons. But they would need impressive reach too in order to get around the length of Smaug's tail and claws. Which means the most epic battle axes, pikes and war hammers ever made.
These weapons would probably be impossible to effectively use with shields. Plus, the jaws and claws of an animal this large would probably be able to get through the shield or simply knock the soldier away. So shields would likely be done away with. But their special built plate armor would provide a good enough level of protection so shields would not be needed to the same degree.
Remember the hollow bone issue? Well, we have now two vital areas to hit here on Smaug. His Caudofemoralis Longus muscle and the wings. So a team with both hammers and axes would be extremely helpful. The ax team would aim to get at the base of the tail to sever that muscle. Those with the hammers would aim to hit as close to the wing's shoulder bones as possible to break the wings. This would maximize the ability to cripple Smaug. Then the pikes could be used to hit eyes, the heart or possibly through the skull.
Basically, the weapons available to any dragon are powerful but long range even for melee weapons. They are like pikes and spears to a degree. These are super deadly if you remain past the tip. Get past it, say by successfully batting it aside, one can then rush in and kill the person. Effectively, the goal for the melee units is to get in closer than the ideal range for Smaug. Too close and it becomes too difficult to see and move properly to hit attackers.
Both ranged and melee options would be wise to use chemical warfare. Poisons can be attached to the blades of the weapons so that any bleeding induced will slowly kill the dragon. This would allow the key immobilizing blows to be landed, then the troops retreat to safety. But this would need to be a powerful toxin to be effective. After all, not much can be fit on a blade and dragons are massive. However, botulinum toxin kills 50% of victims at doses of 1 billionth of a gram per kilogram of body weight. So should some similar toxin be used, Smaug would be seriously slowed down or possibly killed after the first opening strikes. Even if Smaug does not get exposed to enough to kill him, some degree of paralysis can be expected.
Once that happens, it is essentially game over. Mordor's proxy army cannot be expected to successfully carry on after its commander, entire air force and heavy artillery are wiped out at the same time. Especially when the other side has tactical bombers that can attack the remaining infantry with total impunity. The orcs would be caught between the eagles in the air, dwarves and north men in the Lonely Mountain and elves outside. Orcs would be particularly vulnerable in this situation as they require a strong man to force cooperation.
The result is the eagles would hit hard any mass formations from the air while dwarven phalanxes would sally forth on the ground. At this point, the mass formations needed for the orcs to effectively resist would be broken entirely. Which would then leave the attacking orcs quite vulnerable to the remnants of the Dale militia and the elves. In all likelihood, all the orcs would be wiped out.

Outcome

This was conducted by Mordor before Smaug was at full maturity. Nor was his supporting armies fully ready for combat either. Plus they were up against the dwarves. They would be fighting in an area their war fighting is optimized to fight on against enemies they are optimized to fight. They would be allied with another highly motivated faction (Dale's refugees). The other two factions would be quite wells suited for dealing with dragons. Basically, the battle would start off with a lot of sudden successes for Smaug's forces, but would ultimately be a major defeat.
Since I doubt that the attack would penetrate the Lonely Mountain, Dale would be the only area with serious damage. The palisades covering the river would most likely be totally burned. As would most of the interior buildings. But the main outer wall would be mostly intact. The thing about fire and explosions is it needs to get inside something to do massive damage. Pack a bomb in the middle of the walls and you get what we see in Helm's Deep. Just place it next to it and possibly some scorch marks and scratches are more likely. Here's another reason why I think Smaug would have issues getting inside. And partially why Dale will see a full recovery quickly - a key defense remains.
Smaug's attack will mean that the dwarves would first spend heavily on the reconstruction of its major trading link. Secondly, the leadership of the Lonely Mountain would likely start to get a little arrogant. It would see that it just took down one of the major threats that had dogged it for years when it was trying to colonize the Grey Mountains. So it would likely retry.
Then there is the simmering issues between Mirkwood and the Lonely Mountain. The presence of troops might be left outside to help rebuild Dale and/or threaten the Lonely Mountain. Then, Mirkwood could open up negotiations over spheres of influence in the area. They could play on the fact that they came to the aid of the Lonely Mountain despite historical animosity. Settlement could be built around the dwarves stopping their forestry in Mirkwood. In exchange, Mirkwood could offer to maintain the road, allow dwarves to pass through and keep the spiders off.

Aftermath

This would mean sending more colonists up there with the dwarf raider type units operating as dragon hunters. They would be granted essentially Letters of Marque. In this set up they would organize in private groups under the direction of profit motivated private citizens. Most likely middle class dwarves and noble second sons who likely have few other options for the lifestyles they want. Probably the government of the Lonely Mountain and Iron Hills would provide training and equipment for those who work with them. The government would grant the mining rights around the area where they kill a dragon and their treasure hoards to those bands of dragon hunters. In exchange for this, the hunters would probably be required to send a portion of the hoards back to the government that commissioned them. Then they would have to pay a nominal amount in royalties every year and recognize the commissioning head of state as their sovereign.
The problem with the Lonely Mountain's colonization efforts is two fold. First, Sauron would want those dragons for his army. Second, he would have orcs and trolls in this area that would be wiped out too if this progresses. So he would try and counter this. But he himself is not already strong enough to do so. The result would be a push for whatever dragons and orcs in the area to coordinate a resistance. Probably under the command of the Wraith who coordinated Smaug's attack in the first place.
Brutal fighting would take place. We are talking ambushes and massacres by both sides. But this war would be much more favorable to the dwarves. But the presence of the Wraith would keep things from firmly becoming a dwarf victory. I think that this would be a long running conflict that would probably continue until the final expulsion of the Wraith from the area. That would come later though. But it would happen.
Most likely, the defeated wraith would be too disgraced to be left in a major command role for the foreseeable future. It would be sent to handle the intelligence activities exclusively. Which means the corruption of Saruman and the hunt for the One Ring. Embedded in this would be the hunt for and capture of Gollum, searching the Shire and the hunt of the Fellowship.
Also important would be the response of Mirkwood. Remember the elven use of humanitarian aid as a foreign policy tool? Well, now that begins to bear on our story. The refugees would get an offer resettlement aid and some reconstruction assistance. Now, remember that Dale would be rebuilt quite quickly due to dwarven investments and the main the threat eliminated. So it is unlikely that many would. But one of the side effects of the attack and the resulting low intensity fighting in the Grey Mountains, some would certainly.
With the numbers we have, it is entirely possible that Lake-town can be colonized with these refugees. They could then be able to turn their new homes into an economically viable settlement. The fishing and boating industries would naturally still be there. As this area is clearly in Mirkwood's sphere of interest, the trade and security links there would remain. The main difference is there would be Dale and the Lonely Mountain as other trading partners.
Over time, Lake-town would probably grow. Not so much because of economic expansion but as a site of Middle Earth's Underground Railroad. Gondor, Dale, The lonely Mountain and Easterlings would all be slave states and be close to Lake-town. Then, Mirkwood would be a solid place to escape through. Might even provide state support.
This would allow some sort of balancing. A trading point that allows Mirkwood to bypass the Lonely Mountain controlled trade routes would be useful. So too would be the aid Lake-town would provide in making the Underground Railroad more practical. This would undercut the Lonely Mountain's economic power while keeping Mirkwood's involvement more hidden.
Plus it would serve as a wedge to split off some of the Northmen. After all, they might not like slavery at all, but feel loyal to Dale because of its importance. Now, with a new city forming under Mirkwood's protection, there is an alternative. One that could serve as the basis for the return of the old kingdom of Northmen. So many of the local villages might begin to shift away from the Lonely Mountain towards Lake-town and thus Mirkwood.

Conflict Type

Military Campaign

Battlefield Type

Land

Conflict Result

Defeat of Mordor