Slitherine

In the maingame, I used a strat-bomber on top of the fort which stayed there and by a miracle, the ammo of the fort went down from 30 to2 or 1 in a few turns. Then I had a combination of artillery and pioneers or less valuable auxillaries to crack the installations.

However, in the '39 DLC, this doesn't seem to work, are the strat-bombers to weak?
In both scenarios with Modlin on the map, this was like not a piece of cake.

Have the mechanics been changed?
Any experince top share, guys?

The only significant change is that suppressed forts do not surrender when suppressed in PzC, but ammo reduction of strategic bombers should be about the same. Experience plays an important role here, inexperienced strategic bombers are much less effective.

Pioneers are usually very good against forts, as well as paratroopers - they both have a bonus when attacking forts. Suppressing them with artillery is also useful, in particular StuGIII and similar units are good against structures.

Modlin is really strong, but you shouldn't have too much trouble and not need a special tactic.