Yes, it takes a little practice but especially with the US 60mm mortar and also the 81mm you get a semi-indirect fire effect from a defilade position. That means you position your mortar just behind a ridge. That way only other artillery will be able to get you. This mission had two purposes I wanted the Germans to reveal some of their position. Be aware do always combined arms. With a human player it is not that easy but the AI is pretty dumb. Yes, for proper indirect fire your mortars need a radio nearby. Another reason to use the direct fire mode by carefully selecting the terrain. Your ammo is soon wasted by spotting rounds.