The offset square grid is an interesting beast for sure. There have been a number of blog posts about the advantages and disadvantages of various grids – Bob Cordery also covers their use in his Portable Wargame series of books – but I personally think the offset square grid has traditionally been the poor relation of the hexed and conventional square versions. I know that they have featured with some ancient naval rules and I seem to recall a set based on the Russian Civil War using the offset grid but that is about it (and I stand to be corrected). I believe that depending on you orientate the grid (horizontally or vertically) you can better represent the battlefield of your chosen period. I think that using such a grid horizontally (like a brick wall) suits the ‘linear’ or traditional horse and musket period very nicely whilst if you use the same thing vertically you appear to have a greater sense of depth and so would be better suited to the mechanised period. Another advantage of the offset square grid is the ease of making terrain based on the edges of the squares – it is easier to cut right angles than the sixty degree versions of the hexes!