“The Wolfenstein Challenge” – “Partisans” [2nd campaign, 3rd mission]

What caravan? It tells me to conquer a city, but there are a lot of soldiers there... It's impossible.

The caravan appears after capturing a city.

There are indeed many soldiers, but capturing it is not a problem.

You just need:
Machine Management up to a rapid-fire ballista,
Defense up to readiness

And about 600 spear throwers (improved + unimproved).