Sunday, October 25, 2015

Siege 101

The central stratagem in Illyriad PvP is siege. Nothing sends your enemy a message like a well-appointed set of catapults at his doorstep. In this post we will discus the principles of sieging in Illy. 

The Basics

You have built up your barracks up to level 20, completed siege encampment and war machines research, borrowed a handful of siege blocks from your neighbor and built siege engines out of them. You are now ready for mayhem and destruction.

You pick a city on the map, click on it, choose “send army”, and choose “siege”. You will be offered to select a tile near the city on which the siege camp will land, and set the time for occupation. That's right, instead of attacking the city directly you will be occupying a spot next to it, like an occupying army does.

Here is what a siege camp looks like on the map. It is different from an occupying camp and a blockade.

After your siege army lands, there is a 12 hour period before bombardment starts. As your siege engines fire they will destroy buildings in the city thus reducing its population. When population is reduced to 25% of what it was at the start of bombardment, you will be able to storm and raze or capture the city. Mission accomplished.

You can check out who is sieging whom in Illyriad Herald.

Why Sieging is Difficult

After days of waiting, your army finally has arrived to the gates of your enemy's city, only to be completely wiped out by an army 1/6th its size about an hour later... True story!

There are several aspects of Illy mechanics that favor the player under siege, not the sieger:

1. Attack units (cavalry and infantry) have higher attack points than defense points of any unit in the game that a player can build, making defenders inherently weaker than attackers. Somewhat counterintuitively, in a siege camp you are playing defense, not offense. Furthermore, terrain modifiers can further increase the differences between defense and offense.

2. Siege engines have a very slow speed. Your enemy may have several days' or even weeks' worth of notice.

3. Launching a siege is not unlike launching a rocket into outer space. There is no way to adjust it, move to a different square, or increase its size (other than send additional armies). Thus, when sending out the siege you have to plan ahead of time for defense against attacks from multiple cities of your opponent, his alliance mates, and sometimes other players who decide to jump in.

4. Your opponent will be able to rebuild his city under siege in order to increase its population and buy more time for clearing armies to arrive from longer distances.

This is why sieging is not a one-player show. It involves coordination between multiple armies and players, planning everything ahead of time, and exploiting any weaknesses that your opponent may have. 

Anatomy of a Siege

Here is what you need to have a shot at a successful raze or capture:
1. A siege army that has a large amount of offensive troops (infantry or cavalry) and both wall and city siege engines (rams and catapults). Wall engines are often forgotten, but they are essential for reducing the city's defenses. A level 20 wall adds a 115% bonus to defense of the troops inside the city. When you reach the raze population level the army will need to storm the city. If your army remaining after 24-30 hours of attacks is not sufficient to defeat the troops in the city the siege will be aborted.

2. A defensive camp is set up on the same tile as the siege, to protect the siege army. This consists of multiple armies with mostly defensive troops (spear and bow units and sometimes infantry), sent to occupy the square on which the siege will land on.

3. A blockade is set up on a different tile, also with defensive troops, for intercepting vans with basic resources that the player may attempt to use for rebuilding the city.

4. Ideally, both the siege camp and the blockade should be set up on tiles with terrain that favors defenders and penalizes attackers, such as a mountain, buildings, forest or hills. Anything is better than plains! 

5. Attacking armies are sent to both the siege and the blockade tiles. If your opponent knows where the siege and blockade are landing (by scouting or because there are obvious bad tiles) he may attempt to set up defensive armies there, to force your defensive troops into attack mode and incur big losses.

6. Clearing armies are sent to attack the city with two purposes: 1) to clear the city of any troops; 2) to diminish the amount of basic resources available to the player for rebuilding.

7. Magic attacks are used to reduce the city's food supply (blights and a basic resource spell to replace the food spell such as gift of wood). This works well for high-population cities that rely on the food spell.

8. Various diplomatic unit attacks are used to help with taking out basic resources (t1 thieves), kill reinforcing commanders (assassins), and frustrate the player's rebuilding attempts (saboteurs). Diplo attacks are an icing on the cake, and depending on your opponent's sophistication they may utterly fail.

Timing is Everything

It is paramount that all the armies arrive to the camp in sync and land in the correct order. Pre-clearing armies to the tiles should be slightly ahead of defensive troops, followed by defensive armies, then followed by the siege army (with intervals no larger than 1-2 minutes).
Your reinforcements have arrived.
Clearing of the city should start after the wall is reduced. In an ideal scenario this happens several hours after the start of bombardment. Thus, the earliest clearing armies need to be timed to 16 hours after landing of the siege. It is effective to land a clearing army each hour right after catapults hit, to remove basic resources that get salvaged from demolished buildings. Heaviest clearing hits should land by the expected raze time, potentially boosted with assassins. Magic is used after bombardment starts.

The Bottom Line

Take advantage of favorable terrain and plan for overkill. Your siege must survive for at least 24 hours. To ensure that it does, it needs to be supported by occupying defensive armies, a blockade, and well-timed clearing forces. When the city's population reaches the raze target your remaining siege army must be big enough to deal with troops remaining inside the city.

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