Age of Empires IV: Anniversary Edition

I attained this while working on my Rus Mastery. The odd thing is that I constructed 'Fortified Palisade Wall' from the Age I tab (Dark Ages) during my skirmish and it unlocked just fine.

This might be a bug or intended as these "walls" arent as strong as say the stone walls the English possess.

My settings were suboptimal as I was playing for the challenge but I'm sure this can be attained quickly using settings others have been posting (1 AI, Large Map, Wonder only Victory condition and Rich starting materials). On Easy AI, I didnt really have much competition when building the Wonder. The AI stayed in Age II while I was in Age IV. Worst part was defending a rather large wave of Spearmen.

Note: There currently seems to be a BUG (or working as intended "feature" to prevent save swapping) that disables achievement upon loading of a saved game. If youre going for this achievement or others (even Mastery steps), Do it in one sitting. Fair warning :D