How did you pass the train cannon?

[Sparky Harold]

Only one cannon can hit it, can anyone share a how-to video

[lefiath]

Place lvl 3 mortars around it on those positions, and help out with the whippet tank - that's the only way I've found.

[Samoth]

You have planes as well right? Those have pretty heavy bombs, and the automatic weapons can do so damage also. Or possibly if there is one large pad just close enough for artillery. Get those on Lvl 2 or 3 and it may swing it your way.