Soldiering
From the Galactic Civilizations Wiki
Soldiering is the strength of soldiers in a particular race's army. Soldiering allows planetary invasion to be conducted in a more efficient manner, resulting in less friendly losses for more enemy kills.
Soldiering can be improved via race bonuses and certain research technologies. With research in Planetary Invasion tech branch a player also gets access to several invasion tactics, that cost money and may destroy improvements or decrease the planet quality, but improve chances of successful invasion. However, evil-aligned races can construct the No Mercy Invasion Center, which negates the cost of all invasion tactics.
There is a Planetary Defence sub-branch which allows the building of Planetary Defence improvements. There's also 30 points of Soldiering bonus spread across three techs, which can be used offensively or defensively.
After researching Stellar Marines it is possible to construct a Tir-Quan Training center, a Galactic Achievement which improves Soldiering by 25.
Note some AI races (Yor and Drengin) have good starting soldiering bonuses, but they still can not invade planets without the Troops Module, which is made available by researching the first technology in the Planetary Invasion branch.
