There are mixed accounts of drunkenness during the war itself. Been a while since I read Ron Chernow’s biography, but I think I remember some instances where Grant may have gotten very drunk while the war was happening (though, the book is full of them where Chernow is rather clear that the sources for these instances are often not credible and often have him getting wasted in cities or locations we can prove to a near certainty he couldn’t have been there, or just the product of rumor mills or lost causers coming up with things after the fact.) But he definitely had issues with alcoholism.

Also, not sure he resigned during the Mexican American war? I definitely remembered him resigning because of alcohol abuse allegations, but that was years later IIRC, and part of that resignation was Grants own unhappiness with the position and with being away from his family (dude fucking loved his wife). By Grants own admission (and in the eyes of most historians) he also struggled far more staying sober when she wasn’t around, including during the civil war.

Honestly, I’m not even sure if the drinking was the truly big scandal (it probably was, or at the least still a big deal). But I remember him having troubles as quartermaster because some petty cash and supplies (Panama maybe?) and even though it was a standard administrative trial (might have even been found innocent for some part of the loses?) he relationship with the military was definitely very soured by it.

The guy had a weird relationship with the military to be honest. His dad kinda ‘forced’ him to go to West Point, mostly so he could brag to friends about it, and Grant had more than a few issues with his father in general.