After their defeat in the Rebellions, the very concept of krogan leadership was discredited. Where a warlord could once command enough power to bring entire solar systems to heel and become Overlord, these days it is rare for a single leader to have more than a thousand warriors swear allegiance to him. It is speculated that their instinctive aggression and territorial nature prevent the krogan from forming any kind of centralized government or parliament that is not based on fear or obedience.
The krogan homeworld of Tuchanka is divided into multiple nation-states, including the Republic of Ghurst, which was embroiled in a rebellion in 2185.
Traditional krogan tactics were built on attritional mass-unit warfare. Equipped with cheap, rugged gear, troop formations were powerful but inflexible. Command and control was very centralized; soldiers in the field who saw a target contacted their commanders behind the lines to arrange fire support.
Since the genophage, the krogan can no longer afford the casualties of the old horde attacks. The Battle Masters are a match for any ten soldiers of another species. To a Battle Master, killing is a science. They focus on developing clean, brute-force economy of motion that exploits their brutal strength to incapacitate enemies with a swift single blow of overwhelming power. This change of focus from mass-unit warfare to maximal efficiency has increased employment demand in the fields of security and "muscle for hire." Due to the unsavory reputation of the krogan, most of these jobs are on the far side of the law.
Battle Masters are not "spit and polish," but they do believe in being well-armed and equipped, preferably with a gun for each limb. They are callous and brutal, but methodical and disciplined. They use any means at their disposal to achieve their goals, no matter how reprehensible. Hostage-taking and genocide are acceptable means to ensure a quiet occupation with few krogan casualties.
Biotics are rare among the krogan, especially since the practice of surgically creating krogan biotics has been discontinued (due to the high mortality rate). Those that exist are viewed with suspicion and fear. The krogan see this aura of fear as a useful quality for an officer, and often promote them. Combat drones and other high-tech equipment are likewise in short supply.
Krogan military doctrine has a different take on what "scouting and reconnaissance" means. While other races' scouts prefer stealth and discretion in carrying out their tasks, krogan scouts instead opt to deal psychological warfare when they find the enemy by way of occasional harassment or intentionally exaggerating their numbers. The reasoning is that it is a lot easier to count enemy numbers when some of them get blown up.
Weapons developed by the krogan include the Graal Spike Thrower shotgun and Striker Assault Rifle. The Graal was designed specifically for hunting thresher maws, and so has predictably grisly effects when used on humanoid targets. The Striker is a fully-automatic weapon that fires high-impact explosive slugs with high recoil, making it a difficult weapon for non-krogan to keep on target despite it being designed with them in mind. Krogan also use a large infantry fighting vehicle named Tomkah.
The krogan once possessed a powerful fleet that included many dreadnoughts. Since the end of the Krogan Rebellions, however, they have been demilitarized, prohibited from constructing warships. This ban is enforced by the Council Demilitarization Enforcement Mission arm of the Citadel Council, which maintains garrisoned outposts throughout the Krogan DMZ. Every few years, another krogan warlord violates the ban, but usually an alliance of rivals ends his dreams of hegemony before Citadel forces even have to fire a shot.
Relics of the Krogan Rebellions, such as defunct long range ground-to-space anti-ship batteries that dot Tuchanka's surface, serve as monuments to the krogan's past glory and military might, but have little practical value.
Krogan are divided into numerous clans. Membership in a clan allows a krogan to own property, join the army and apply to serve under a battlemaster. Clan diplomats represent the strength of their people to other clans, and thus make it their job to look intimidating lest their clan be targeted for conquest.
Young krogan undergo a rite of passage that is overseen by a shaman respective to the clan the krogan wishes to join. In Clan Urdnot, this rite consists of battling various wild fauna on Tuchanka, ending with an encounter with a thresher maw. Merely surviving for five minutes is considered proof of worthiness, but killing the thresher maw increases the initiate's prestige and standing. In Clan Nakmor, it's claimed that it isn't so much a rite of passage as a "death trip", and surviving entails membership into the clan.
Few outsiders have seen a rite of passage take place, even though there are no rules in krogan tradition that state that a non-krogan can't help with the undertaking of the rite by acting as the participant's krantt.
Known krogan clans:
Clan Bragus - Bragus Thul plays as a quarterback in North-American-Union-Rules football.
Clan Dahmbra - one of several clans with individuals that joined the Andromeda Initiative.
Clan Drau - Drau Sorze is a "ruzad", or "judge", in the Republic of Ghurst on Tuchanka.
Clan Forsan - this clan's leader declared being hit by pyjak dung is grounds for executing the trader responsible for introducing them to Tuchanka.
Clan Ganar - Ganar Wrang, an exiled krogan battlemaster, founded the Blood Pack mercenary group.
Clan Gatatog - led by Gatatog Uvenk on Tuchanka.
Clan Graken - Graken Dhal, a warlord, involved in the bombardment of Digeris during the Krogan Rebellions.
Clan Gulnaz - one of several clans with individuals that joined the Andromeda Initiative.
Clan Hailot - clan leader Hailot Wrund controlled Garvug prior to the corporatist invasion in 2185.
Clan Jair - one of several clans with individuals that joined the Andromeda Initiative.
Clan Jorgal - a clan known to have one of the longest krogan breeding lines and oldest bloodlines.
Clan Jurdon - an enemy of Clan Urdnot on Tuchanka.
Clan Kariss - one of several minor clans with individuals that joined the Andromeda Initiative.
Clan Khel - Khel Burrum is a krogan competing at Pinnacle Station.
Clan Kohrr - one of several clans with individuals that joined the Andromeda Initiative.
Clan Kormer - one of several clans with individuals that joined the Andromeda Initiative.
Clan Korten - a clan known for making klixen-roasted varren jerky with their own signature pyjak sauce.
Clan Quash - Quash Hurgott is a Blood Pack commander.
Clan Raik - source of the word "Aralakh", meaning "Eye of Wrath", which became the common name used by the galaxy to refer to Tuchanka's star.
Clan Ravanor - the clan runs a mining operation on Tuchanka; Warlord Ravanor Tusk is a clan member.
Clan Shath - Shath Norda survived a trip to the planet Kruban.
Clan Strogjaw - Strogjaw Grog is a member who joined then deserted the Andromeda Initiative.
Clan Talyth - a clan that attempted to rebuild a dreadnought on Tuchanka with the help of turian duarch Ellis Valterus.
Clan Thax - the clan of krogan businessman Thax Vorak.
Clan Wik - one of several clans with individuals that joined the Andromeda Initiative.