1866, published in 2010, is the last of the original Grand Tactical Rules trilogy for the mid-19th century wars of transition. It covers the Austro-Prussian War in Bohemia, the “German War” by Prussia and its allied contingents against Austria’s Federal German allies, and Italy’s third War of Independence against Austria in northern Italy.
The basic Grand Tactical Rules were modified to accurately reflect each side’s strengths and weaknesses – Prussia’s formidable fire doctrine and Austria’s fervent adherence to shock combat – while giving each side the means to win within these historical parameters. The core rules, however – the command control, movement, fire, melee, and morale mechanics – are still as they were in the original 2001 vintage 1870 rules. If it worked, it hasn't been touched. As with the other Grand Tactical Rules, there is an updated quick reference sheet (and rules summary) for the revised, quick-play 1866 rules here. This will enable much faster resolution of 1866 battles using the new 1871 fast play improvements.
In addition to the basic “grand tactical” scale, half and quarter-scale variants give 1866 gamers the option to play smaller battles, with just two or three divisions per side down to engagements involving just a few regiments.