Armies tend to be fairly small in Dune: Spice Wars. The hostile environment of Arrakis means it's necessary to choose quality over quantity. With only a handful of units at your disposal at any given time, besieging an enemy capital can feel like an incredibly daunting task.
Capitals, or Main Bases as the game calls them, require a prolonged, concentrated effort to bring down. The investment is worth it, however, as successfully taking a capital will remove its controlling player from the game. Knowing how to approach a capital siege is the surest way to make sure you win.
Updated on September 14, 2023: With the release of Dune: Spice Wars out of early access, we've updated this guide to include new tips for the biggest military undertaking available in the game!
Main Base Defenses
All four factions' capitals have identical stats, though certain districts can improve their defensive capabilities. A standard capital has twenty thousand Health points and twenty points of Armor, meaning it will take a huge amount of firepower to bring one down. A Main Base does not gain or lose any combat ability as its Health degrades, but it's important to note that there is absolutely no way to restore a capital's Health once it has taken damage.
Capitals can be buffed by structures such as Enhanced Fortifications. Be sure to check the base's current status before launching your attack!
Every capital is equipped with a single missile launcher at its center, which deals heavy AoE damage with every shot. The capital's defenses have a long enough range that they can hit targets just outside the capital's Region. An unsupported army will eventually fall to the barrage of fire from a Main Base, even without defending units, and the damage will start to pile up before the attackers can take their first shots.
Preparation
Attacking an enemy capital is not something to be done on a whim. If you're going to make an attempt, you should be prepared to see the attack through - otherwise you're just throwing troops away. In general, you should only attack a capital if the owning player is already in a weakened state. Rebellions, loss of territory, or a bad session in the Landsraad are all things that can make a faction vulnerable.
Once you've decided it's time for a faction to depart Arrakis for good, the best way to prepare is to conquer at least one Region adjacent to their Main Base. Not only does this provide you with a necessary staging area from which to make your assault, but it also deals a devastating blow to the target's economy. Even if the conquered Region has economic bonuses or all-important Spice deposits, it's critical that you develop your newly-acquired Village with Military buildings. You can tear these down and replace them with Economy and Statecraft buildings after the battle.
If possible, avoid invading Villages within the range of the capital's guns. Otherwise, even if you manage to take the Region you'll be shelled constantly.
After taking a Region next to the enemy capital, immediately construct a Missile Battery to defend your latest acquisition. You can expect your opponent to throw everything they have at removing you from their doorstep, so you'll need to be ready.
Once the Missile Battery is finished, build a Military Base to provide your troops with a Power bonus while defending the Village and, critically, during the final assault. Last, purchase a third building slot and construct an Airfield so that new recruits can be brought from your own capital to the front lines quickly. This last step, of course, is unnecessary for the Fremen who rely on Worm Riding for fast travel.
It can be tough to build up the necessary Authority to annex a region next to an enemy base. If push comes to shove, setting up your assault from two regions away works, even though it isn't ideal.
Attacking The Enemy Capital
Once you've entrenched your position, wait for the right time to strike. Watch for your opponent's troops to be distracted by events elsewhere on the planet, or for a particularly devastating Landsraad Resolution like Architectural Surveys to hit them. While you're waiting, position a minimum of three Melee units and two Demolition units (more if you're playing on a Difficulty above Normal) at your forward base, and prepare the Operations Supply Drop and Defense Sabotage from the Infiltration screen. If you have sufficient resources, also prepare Defense Breach
When the time is right, order your units to attack the Main Base. Protecting the Demolition units is critical here, as you need them to wear away the capital's Armor if you hope to do any significant damage. If the enemy player has troops in the area, use Gear Sabotage and focus your attacks on eliminating them quickly before turning your attention to the city itself.
At the same time, start training and Shuttling troops to act as reinforcements. Have them wait in reserve by your forward base to replace units that fall or retreat.
Air units are particularly vulnerable to missile fire from the base. Keep them far from the fighting, and instead rely on them to intercept reinforcements or to dissuade attacks by other players while the bulk of your army is occupied.
Spread your troops out to minimize the damage from the capital's AoE attacks, but keep everyone on the side near your military base so that you can retreat as units become damaged. When one or more units drops to about half Health, use your prepared Supply Drop to give them enough regeneration to pull back to friendly territory, replacing them with a reserve unit.
Always be sure to immediately prepare new covert missions when you use them - you may need to use them several times throughout the fight. Continue rotating your units so that there are always healthy troops maintaining the assault, and the capital will eventually fall.
If you need to withdraw your troops entirely due to unexpected reinforcements or an attack on your own territory, you can renew the attack later - even if the capital doesn't fall in the first siege, dealing five to ten thousand damage is still a significant blow!