Editing Warhammer 40,000/9th Edition Tactics (section)

===Morale 101===
A unit can lose additional models in the morale phase; failing a morale test by rolling over your Leadership with 1d6 + the number of casualties the unit has taken this turn means one of your models flees.  A morale test of 1 always passes. If you fail the test (i.e. a model fled), you take combat attrition tests: roll for every remaining model in the unit, applying -1 to the result if the unit is below half strength after that model was removed.  For each 1, another model will flee the unit.  These rolls are "Combat Attrition Tests".  After that, if your unit is not in coherency, you must choose models to flee until the unit is in coherency.

Fleeing means that a model counts as destroyed, but does not trigger any rules that would respond to its destruction when it flees - instead, it will trigger rules that respond to fleeing. 

*The morale phase happens after the psychic, shooting, and assault phases and any casualties from those phases are added together when testing morale.

====Morale Mathhammer====

In general, a unit with Leadership "Ld" that has taken "C" casualties this turn will pass a morale test with the following odds:
*Ld >= 6+C:  6/6 (automatically passes)
*6+C > Ld >= C+2: (Ld-C)/6
*C+2 > Ld:  1/6

For example, Ld 10 means a unit with 5 or fewer models will always pass a morale test unless some other rule intervenes, because it can't take more than 4 casualties and still take a morale test, and after 4 casualties, the final member will not have to roll.  On the flip side, for a very large unit, say, 30 members, any practical Ld value will quickly become meaningless as casualties rack up, and you'll end up relying on the baseline 1/6 odds of passing.

If a unit fails, it will lose 1/6 of its remaining members if it is still at or above half strength, or 1/3 otherwise.  Due to this, even starting unit sizes are ''generally'' more efficient than odd ones: here is how many casualties several unit starting sizes have to take to take combat attrition tests with a penalty (i.e. before the morale test that must be failed in order to proceed).  Remember, a unit at 1 more member than below half strength will take combat attrition tests with the penalty, because that 1 model will flee before the tests are taken.  A 0 means the unit cannot take combat attrition tests.

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And so on; in general, going from an odd number to an even number of models increases the number of casualties you have to take to be below half strength, while going from an even number to an odd number does not.  The only exceptions to this are going from 1 to 2 (neither unit will ever take a combat attrition test) and going from 2 to 3 (a 3 model unit can lose its third member to a combat attrition test).