Why do units lose ini experience bonus when mass attacked?

[CrimsonStorm]

I have 1 109G next to a MiG 3. On the combat expectation I am Initiative 10, experience bonus +3, Effective Initiative 13. He is Initiative 10, experience bonus +1, Effective Initiative 11

I fly a second 109G up on the other side of him. I am still Initiative 10, experience bonus +3. However he has now changed to Initiative 10, mass attack -1, Effective Initiative 9

What happened to his experience?

[deducter]

This is a special case. The reason is that initiative bonuses from experience are calculated at the very end, at the effective initiative. In your case, the mass attack reduced the effective initiative of the MiG-3 to 9, when it can no longer gain the bonus.

Another example is panzers in cities. Your 4 star Panther does not have any bonus to initiative when stuck fighting in close terrain.

Another example is bad weather, which sets the initiative of all units to 1.

[CrimsonStorm]

Hmm I notice my infantry also don't get an init bonus when attacking towns. Odd I thought they would not have been affected.

[deducter]

Hmm I notice my infantry also don't get an init bonus when attacking towns. Odd I thought they would not have been affected.

Your infantry don't get an initiative bonus in general because the threshold is usually very high. It doesn't matter if it is a city or in clear terrain. Since initiative bonuses are 10% per star level, and the game always rounds down, for a grenadier you need 4 stars to get an initiative bonus and even for a fallschirmjager you need 3 stars. Hence mass attack with infantry makes a big difference in close terrain.