I was playing a game recently where there were 4 civs left, me, the Spanish, the Mongols and the Greeks. I was invading the Greek island casually, with Alpine troops and Howitzers and Artillery. Of the computer controlled civs, none had gunpowder or conscription and their most advanced units were Knights and Legions.
I fortified an Alpine troop next to a Greek city and backed up a couple of Artillery. Next turn when I attacked, the first Artillery got creamed by a RIFLEMAN fortified behind walls. I checked through the UN and discovered that no civs had gunpowder or conscription still. And they hadn't bribed one of my units earlier either and I certainly hadn't given it to them as a gift. They just got given a free Rifleman. Not fair at all.