The rules used were Hail Napoleon - our house variant of Hail Caesar for the black powder era - with a extra few tweaks we use in large historical battles. Some tactical options are simplified (with 50+ units a side the players have plenty to think about without concerning themselves with what individual battalions are doing). We halve our standard ranges (so 6" for muskets, 18" for artillery) so they are a better match to the ground scale. We maintain the standard move rates (0-3 times 6" for inf, 9" for cav), but consider each turn to represent twice as long a time to compensate.
We used 15mm figs in this battle for 2 reasons:
1) We don't have any figures for 1704, but our 15mm 7 & 30 Years Wars figures pass pretty well as long as you don't bend down too close, so a much better visual match than 28mm subs.
2) They are much less out of scale with the terrain than 28mm figs, so make for a better simulation in a large battle with a small ground scale.
The battle front was 7.5km long so a ground scale of only 400mm per km was required to allow it to fit on our preferred 10'x6' table configuration. This scale also suited the available number of figures. At this scale, the 150mm wide units represent brigades of 1500-2000 infantry or 600-900 cavalry (varying because the number of ranks in the formations varied between the several national armies involved). The Command Groups are divisions of 3-8 units & closely follow the historical order of battle though there is some simplification of the OOB below that level (variations in numbers, size & quality of individual battalions & squadrons within command groups add complication we don't need when there are so many). When deployed historically on the table, our figures matched very closely with Jeff Berry's map so our calcs on the spaces occupied per formation match nicely.
The players tossed off for places:
Tallard = Mike. Marsin = Mark. Chris = Marlborough. Steve = Eugene.
They started the battle in the historical deployment except for a bit of shuffling of artillery batteries.
So our Blenheim reversed history big time. Our Tallard & Marsin seized the initiative, got on a roll, rode their luck & never let the Imperial army recover. They broke through the Imperial centre to split the two Imperial armies apart then destroyed their desperate counterattacks. By the end the French & Bravarians lost just 2 units each. Eugene lost 3 units & had no trouble retreating his force, but Marlborough's army was entirely broken. Alas, no great palace in Oxfordshire for our Malborough.