It's a combination of computer real-time-sim and LARP. Generally (although I don't know about this one) all the players form a number of teams/sides/countries/whatevers, and using - again generally - some sort of resource management system attempt to reach the stars/kill the oppostion/get voted into office/whatever the objective of this game is.
Most often the players are the generals or the politicians or the heads of corporations, and issue orders to their peons, which are then carried out by the GMs. You get the results of your actions and then plan the next thing, etc.
The Grand Strats have been slowlyc hanging over time. A few years ago, they were MUCH more like a large scale boardgame/wargame with attached LARP elements. Dillion's been experimenting though, trying to generally get rid of anywhere there was a hold up in the gameplay waiting for turns, and to cut down the admin work.
Since I've now gone up to KapCon and actually met up with folks in the North Island: this year is a great year to come down to Buckets! We're currently going to be running over three days (plus one evening), which also means that you don't have to put up with two late nights in a row (LARP and Grand Strat will be separated by a day). Although Monday may become recovery day in the style of KapCon.
I can't guarantee that we'll be quite as excellent as Al Shir-Ma - the LARP community at SAGA has died off quite a bit recently. However since I'm writing the LARP (and already have quite a bit written down on paper), if we get a giant influx of LARPers I can definitely write in some more roles for folks.
Welcome to Diatribe, Akchizar! It's really good to meet some Christchurch folk, and have you guys let us know what you're up to in terms of larping. I don't think I got a chance to meet you at Kapcon but hopefully we'll meet at another con soon.
Something between a wargame with larp elements and a larp with wargame elements, with realtime feedback between the two. So you do some larp, take some actions on the board, and panic over the response, with the wargame providing a stream of events into the larp element for the players to respond to. The ur-grand strategy is probably kriegspiel diplomacy, where each country is played by a team of three, typically with a fog-of-war (so your negotiators are also there to gather intelligence on where other people's units are).
They're a feature of buckets; Dillon has made noises about running one in Wellington, but it hasn't happened yet.
Typically, I send the email call for game information for the website in early March, and game information for the website trickles in over the course of March and early April, with the website going up early April. I try to have a full timetable of games available by the time Game Selection opens (on June 1st this year) and this year I'm trying to over-anticipate demand so I don't run around in June with my hair on fire (to borrow an expression from IdiotSavant )
So the short answer is, "by the end of March" - and Ryan speaks truth, 25 is a really good size, we'd love to have you.