As per your request ... some tips ...
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I am not looking at the scenario, Heartbreak Ridge, right now. However, I had played it in both RDOA and HTTR with full order delays.
My approach would be to rebalance my forces such that I would have one armor heavy force and two infantry heavy forces.
The armor heavy force would attack frontally over open ground up the ridge. (If I recall, it will probably be replused once or twice.)
The two infantry forces would attack the Ridge through the woods from East and the West.
Eventually, the Germans will begin to falter and finally fallback to the North as the armor force drives up the middle.
I believe there was some arty. If it is in range, then put it on call, [D]efend, immediately. You haven't got time to waste.
Also, you probably want to command maximum effort from the troops, meaning AGGRO=MAX, ROF=MAX, CASUALTIES=MAX/HIGH ... Lower settings are more appropriate for protracted struggles where you are trying to wear down the enemy. With 12 hours, you only really have one chance to get the job done.
Also, if I recall, I might have sent some armored car companies to circle around and probe the Ridge from the North. The intent was not recon; as this scenario doesn't need any recon. I just simply wanted to harass the Germans. Also, you never know what you might turn up when you approach from the back door. Perhaps, you'll turn up some arty or mortar positions which can then be hammered by your own guns.
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Note: In HTTR, the armor attack will be more effective as it will move to contact and then standoff at the effective range of their main cannons as opposed to immediately attempt to close assault dug-in enemy infantry. Perhaps in RDOA, you might want to delay the armor push a bit so that the infantry advancing on the German flanks can disrupt their positions on the Ridge a bit. Another option would be to have the [A]ttack task marker fall short of the Ridge Peak. And yet another option might be to command the Armor to form a defensive line position half way up the Ridge and stand off. Of course, when the Germans begin to falter, then you will need to issue new orders to the Armor to take the central peak of the Ridge.
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Phil,
Go take that Ridge and send us some photos (screenshots) with yourself astride the Ridge with a German 88mm in the background!
or another screenshot perhaps.