Expansion - beyond-all-reason/springrts_engine_wiki_mirror GitHub Wiki
Expansion focuses on building a large sprawling base. The aim is to capture resources as quickly as possible. With a significant economic advantage, the player can then crush the opponent with superior forces. In most Real Time Strategy games, the ability to expand effectively is required to have a chance of winning against reasonably experienced opposition. Unlike many other RTSes, Expansions in TA are cheap and fast to build, allowing for rapid expansion across the map.
To expand effectively, a balance between military units and resource units must be found. If you build too few military units an enemy raid can destroy half of your base. Build too many military units and your expansion will be slowed down due to lack of resources being spent on expansion.
Many beginners err on the side of building too many military units. They only expand when they have enough defenses to feel confident that an enemy attack will not do any damage. However in most TA based mods, metal extractors can be built cheaply and quickly. A fast and lightly defended expansion can build up a resource advantage, unless the enemy's fast to respond, in which case the metal from your unit's corpses can give him an edge. Enemy raids will reduce this advantage. but as long as you defend well enough to avoid losing large parts of your base, as opposed to a few cheap outlying metal extractors, the advantage will be maintained.
The other error beginners can make is to not build military units early enough. They focus on only expanding their economy during the early part of the game, and then move into a subsequent period building up military strength and massed assaults. This strategy will fail if the opponent rushes or raids early. While the Commander can serve as a deterrent to such attacks, most light units are much faster than he is, and can easily avoid him.
In team games, the normal starting arrangement is to have each team in a line on each side of the map, in a North-vs-South or East-vs-West arrangement. Players then focus on expanding towards the middle as quickly as possible to seize as much territory as they can and deny that territory to the enemy. Once a solid defensive line is established as far forward as possible, any vacant resource spots behind it can be occupied later with little fear of opposition. With several players expanding forward in a line, there is less chance for enemies to slip through the defensive line before it closes. A good player may still find a way through and cause unexpected havoc, or break through with the aid of light artillery.
In a one on one game, there are usually several directions to expand in. A player that expands directly towards the middle as in a team game can find the opponent expanding sideways and attacking from exposed flanks.