[Mobhack]

The number of men assaulting is also a factor, with small numbers (like 1!) having a severe disadvantage over say a section of 7+. Same goes for only having grenades, or no weapons at all. Such units are much more likely to flee in "tank panic". Some classes, like Crew, Headquarters and Arty Observers are also much less likely to have successful assault outcomes than real infantry.

plus if applied to an assaulter:
low morale=bad
low experience=bad
suppressed=very bad
already spotted=bad
unspotted=good
moving=gets worse per hex moved before attempting the assault

However there is always a small chance they may well manage the trick.

The answer is not to blunder about with unprotected tanks in areas where healthy enemy infantry are to be expected. Send your dismounted troops in first, or at least nearby (2-3 hexes) since they can spot infantry better than tanks do. Even APC with mounted infantry are better than nothing. (Vehicles with thermal sights of course are rather better at spotting infantry etc at 500m and less, but even so I would not blindly drive about with them unsupported by infantry). And dust the area with mortar fires or area Z fire before entering to at least suppress elements (S=bad).

Andy