Chivalry 2 (UP)

I have found 2 ways this can be done relatively easily:

Step 1 in either case is joining an empty Rudhelm Siege game through the server search and join the defending team.

Step 2a (Shorter, but more play intensive): Simply kill bots and prevent the siege towers from reaching the wall. This will take 10 minutes total.

or

Step 2b (Slightly longer, but almost 100% AFK): Don't play at all for the first objective. Either your team will win or the bots will capture the first objective (most likely). From here you have to defend the gatehouse for roughly 5ish minutes depending on how long the first objective took. You can sit AFK at the gatehouse and simply kill enemies when you notice the objective is being captured. On average this takes a total of 15 minutes while only having to actually play for about 1 or 2 minutes.