This mission is somewhat broken—and completely loony in relation to the real Operation Market Garden.
It’s broken because, on the German side, flak-20mm guns, MGs, Hummels, call-in CAS, and probably other units are at least partly non-functional. Hummels, for example, will often not fire when you order them to, though they will have a long “cool-down” period as if they have fired. CAS usually won’t show up despite consuming 200 muni points. MGs and flak-20mms will fail to hit or even aim at infantry approaching them slowly across open, flat ground. Even 88s seem blind to many approaching attackers. On the British side, many units including commandos with M-18 recoilless rifles or PIATs are coded to be virtually immortal, and can make themselves invisible at will. The British also have the ability to enter a building and instantly turn it into a garrison with crewed MG.
The mission is loony because it assumes a paratroop/commando assault on Osterbeek (a western suburb of Arnhem) with major artillery support from the south side of the Rhine, as well as a powerful British presence within Osterbeek including a supply of heavy armor (Churchills) that is easily enough to defeat the German force at the outset. This is all wildly non-historical—it seems to assume the British XXX Corps made it to Arnhem and relieved the trapped paratroops; but if they had, Market Garden would have been a success, not a failure.
Overall, the mission plays out as if it was hastily tacked onto the campaign and inadequately tested.
There are three tasks the player needs to accomplish to achieve the win and the mission medal.
To win, the player firstly must prevent the river attackers from capping points so as to connect to the British-held territory in Osterbeek town, and secondly must either cap the VP in the town square or destroy a certain number of British tanks, AT guns and emplacements (triggering surrender).
To get the mission medal, the player must use Hummels (or the prior 25-pdr emplacement on the bluff, if it still exists) to destroy the three British 25-pdr howitzers across the river—and those 25-pdrs are miraculously alert and effective in shelling anything near the shoreline.
Dealing with the river attackers is easiest, and is the focus of the first part of the mission. Build some flak 20mm guns to guard the points near the beach exits. Add some infantry halftracks and maybe a Wirblewind for support. The insanely overpowered Allied (in this case Polish) infantry will eventually attack in overwhelming force, but the attackers are on the clock, and if you can resist them near the beaches, near your base, and in the approaches to Osterbeek, you can easily run out the clock on them (they flee into Osterbeek).
As you are doing that, you’ll also have to deal with some Churchill-led attacks around Osterbeek, but they are weak attacks (three Churchills, one at a time) that regular infantry with schrecks and assault guns, and maybe some mortar halftrack and PzIV support, should be able to handle. Once you can focus on Osterbeek, you can use mortar halftracks and Hummels (you will get a free Hummel and Jagdpanther, but you also can get Hummels via the Scorched Earth commander) with tank/infantry support to take out the British emplacements, AT guns and other high value targets one by one until the British give up. Often the destruction of the Bofors emplacement at the lower left of the town square is the trigger for a general surrender.
During this last mission phase, when you are focusing on Osterbeek, you can take one or two Hummels to the beach or bluff at the upper part of the river and nuke the 25-pdrs across the river for the mission medal. If you lose a Hummel, bring in another.
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