Infantry: Field Fortifications & Buildings

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Infantry: Field Fortifications & Buildings

Post by Mock26 »

Field Fortifications

Have you ever seen these strange looking lines and wondered what they were?


Those are field fortifications. Under regular BattleTech rules they are created by an infantry unit spending a turn "digging in." That rule is not used on this server but some maps come with field fortifications already in place on the map.

Have you ever wondered what benefit they provide?

Any infantry unit inside of a field fortification receives a +2 defensive bonus against all weapons except for flamers and other Area of Effect weapons. In the below images the Firestarter is firing a machine gun and a flamer against the infantry in hex #2318:

Note the +2 for infantry being dug in.

Note that there is no +2 for infantry being dug in.

Additionally, against all weapon types, including flamers, infantry in a clear hex that are inside of field fortifications do NOT receive double damage from attacks. Burst fire weapons, such as machine guns and flamers, still do extra damage but it is not doubled. For example, Machine Guns do 2d6 damage and Flamers do 4d6 damage against infantry. In clear terrain this would be 2d6*2 and 4d6*2 respectively.


Infantry that is inside of a building cannot be directly attacked by units that are outside of the building. Instead you have to fire at the building itself. When you fire on a building with infantry inside then for most buildings some of the damage will be transferred to the infantry inside. This depends on the type of building.

Light Building: 75% of damage to building*
Medium Building: 50% of damage to building*
Heavy Building: 25% of damage to building*
Hardened Building: 0% of damage to building

* In case of fractions damage is rounded up.

For example: If an infantry unit was inside of a Medium Building and was fired up on by an AC/10 only 5 points of damage would be done to the infantry.

Please note that fire at a building needs to be directed at the floor upon with the infantry is on. For example, if a platoon of infantry was on the first floor of a 2-story building and an opposing unit could not fire upon the first floor do to an intervening 1-story building then that unit could not fire upon the 1st floor. If he fired up on the 2nd floor and caused damage it would damage the building only and no damage would be passed on to the infantry. Additionally, if there were two infantry units on two different floors any attack on one unit would not affect the other. Burst fire weapons, such as machine guns and flamers do not do extra damage against infantry inside of buildings.

If a building collapses while infantry is inside of the building they will take damage from the building collapsing and possibly falling damage. Collapse damage is the building's CF at the beginning of the current phase divided by 10 and multiplied by the number of levels above it. For conventional infantry this is then multiplied by an additional 3x for conventional infantry and 2x for mechanized infantry. Falling damage for infantry is as follows (for every 2 levels fallen):

Foot Platoon: 3d6
Motorized Platoon: 2d6
Mechanized/Jump Platoon: 1d6


Field fortifications can certainly limit your infantry platoon's movement by keeping them in place, but they can greatly improve the unit's survivability on the battlefield. Additionally, buildings can offer great cover for your infantry in urban environments, but be careful as a building collapse can easily destroy an infantry platoon.

As always use this advice at your own discretion.

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Re: Infantry: Field Fortifications & Buildings

Post by tehemperorer »

It might be important to note that firing on conventional infantry hiding in buildings still uses (at least, it should) the "Non-Infantry Weapon Damage Against Infantry Table, TW p.216, i.e., an AC/20 fired upon a conventional infantry unit hiding inside a medium building will do 20 damage to the CF of the building and 1 damage to the infantry squad.

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