If you would like to counter early bunkers I strongly suggest:
- An M3A1 Light Scout Car (80 MP, 20 fuel, 2 supply)
- Combat engineers (240 MP, 6 supply)With ROK's flamethrower (60M)
Embark your combat engineers into the back of the M3A1 scout car and flank the bunkers.
As stated above, it would be a godsend if the enemy has spent the bulk of their starting funds on a MG bunker. This would set them back on a lot of tech time meaning that they wont be able to use the pesky panzerfausts, this would allow your fiery scout car to be hell on wheels to enemy infantry. Not only does this counter bunkers and emplacements it is also very effective against mortars and MG42 HMG teams. You must be very careful to try and keep the scout car out of the arc of fire as much as possible due to the fact that it has a lightly armoured frame. Against the AP rounds from a veteran MG42 team its like the butter with a hot knife going through it, if this happens bail and retreat your infantry.
Not only can you burn any infantry to a crisp and destroy emplacements, you can also capture territory with the scout car loaded up with units. This would make the 'rolling front' tactic work very well and would allow you to starve the enemy of resources very early on resulting in a very infuriated opponent. Cheap, reliable and effective.
Another effective way at countering early bunkers are mortars however these require funds for the Weapon Support Kampaneya (240MP 6 supply) and 360MP (for the mortars). I would not recommend using mortars until late in the game when the enemy has tanks or scout cars equipped with auto cannons, these render the first tactic useless unless they are covered by an Divisional Field Gun or at least two squads of conscripts. I do however, agree that mortars are underused
I have not written about how to counter them with tanks because that should be pretty self explanatory and you won't be able to get them early on in a game.
Hope this helps