This article attempts to explain a tactical aspect which is extremely prominent in several SC maps. I believe it applies to all of the maps to varying extents.

In the vast majority of the history of naval warfare the wind was the main means of locomotion for vessels. In all of that time one factor was held to be of paramount importance: the weather gauge. Simply defined, the ship or fleet that is upwind determines when, where and whether or not to attack. Other factors were important, but no commander of any naval force ever deliberately chose to put himself downwind of his enemy. The weather gauge, the upwind position, was of vital importance.

The fact that SC has multiple win conditions creates a similar effect on many maps. You have a target that must be defended, your homeworld (HW), but if you leave the weight of your fleet there then your opponent snatches up the rest of the map and you lose on destiny and a slow deficit of production. If you consider it in nautical terms, the source of the wind would be the middle of the map, which is generally the SC. The player with a fleet at the SC can be said to have the weather gauge over the player whose fleet is at his HW. The player with the weather gauge defends his HW from the front, while the player without the weather gauge must defend from the rear. It's very rare that a player wins a match without the weather gauge despite the importance of cards. This is why vets always stress the importance of "boardplay".

Let's look at Rival Twins, which is probably the starkest example of the importance of the weather gauge in the catalogue of maps:

As in any map the opening turns are about a) taking your share of the minor planets and then b) gathering as many of your voters as possible at the SC. Once cruisers have begun to proliferate and fleets are amassed, the weather gauge is in effect. Let's assume that both players have an exactly equal weight of materiel: 3 cruisers and 3 scouts. The green player (Ferrier) has two scouts at Veddel, one scout at Thrack, one cruiser at Cronk, and two cruisers at Opreak. The red player (Zhik) has his 3 cruisers and 3 scouts in the SC.

Now you might think, "Volcanis is undefended! There are no ships there!" But actually Green is horribly out of position and Red has the full weight of the weather gauge. He may attack Cronk (he will have superior numbers in that battle), he may spread out and take Thrack as well, or commit a larger force there and catch a sole scout or trap several cits there to miss the next vote, or he may go for Vermillion Prime arriving in two turns. Green must defend his HW at all costs, so he ends up backing up even further. He brings his scouts from Veddel to Xorax, his cruiser at Cronk retreats to Opreak.

The position quickly becomes very stark: the SC is a gun. Red has it loaded, Green does not. And because of the nature of the weather gauge, there is no way Green will be able to load it. Once you are out of postion on this map, you stay out of position. If Green tries to advance on the SC through either route, Cronk or the direct 4 jump, he will inevitably leave his HW open to attack.

The outcome is clear, Red, with the weather gauge can take the lower half of the map easily, outproduce Green with the indies and set up a destiny bleed with the extra artifact planet. Green is pinned down at his HW. If he tries to get out he will be attacked. If he doesn't try to get out he will lose slowly.

Many of the SC maps have a very strong weather gauge effect. The player who threatens attack will have freedom of movement across the board. The player who loses the weather gauge will be confined to defense for the rest of the match. And the weather gauge is determined much earlier than you might expect. The first PK (peacekeeper) vote is of critical importance on most maps because of the weather gauge. If you have advanced a cruiser to the SC and won the PK vote and your opponent in his initial expansion has only built scouts and spread them across the map, the threat, as early as turn 7, may be dire. Your opponent retreats, gets locked up on defense and watches his advantage on the rest of the board evaporate.

The moral of the story? Consolidate your forces closer to your opponent's HW than he can consolidate his to yours. Or you can use this simple reminder: FIF, Fleet In Face. That's where it belongs. If you keep your fleet in your rear (FIYR) it won't accomplish much more than anything else you'd find in your rear :) That's the weather gauge in a nutshell. Hope it helps!