Second Star League
|Time period:||3058 – 3067|
|Ruler title:||First Lord|
|Military:||Second Star League Defense Force (SLDF)|
The Second Star League was an interstellar alliance formed by the major and minor powers of the Inner Sphere in response to aggression by the Clans. The Clan Invasion of 3050 had cut a swath of destruction through the Inner Sphere before eventually being stopped at the Battle of Tukayyid, and while the Truce of Tukayyid had bought the Inner Sphere some breathing space it was only a temporary reprieve. After the Jade Falcon incursion of 3058, Inner Sphere leaders met on Tharkad to draft a new Star League Constitution and appoint a new First Lord, the first in many centuries since the end of the original Star League. While the Second Star League would help end the threat of the Clans with the destruction of Clan Smoke Jaguar and the Great Refusal, it did not survive long: on 28 November, 3067, the Second Star League was disbanded following a no confidence vote, triggering the Word of Blake Jihad.
The new Star League Constitution was built largely on the framework of the original, with the important exception of the role of First Lord. While the original First Lords were all members of House Cameron, the new position would be held on a rotating basis, with the leader of each member nation serving a three-year term and unable to serve again until every other nation's leader had already served. The position is also largely a ceremonial one, though the First Lord possess the authority to, among other things, appoint the Commanding General of the Second Star League's military.
The Second Star League Defense Force was created during the First Whitting Conference and prosecuted the destruction of Clan Smoke Jaguar with Operation BULLDOG and Operation SERPENT. Though the ultimate goal of the Second Star League was to create a wholly independent SLDF, due to the small number of so called "core" units, the organization relied heavily upon preexisting units from each member-state. Such units were donated for fixed periods of service and operated per the SLDF Chain of Command. 
- Jihad Hot Spots: 3070, p. 10, "Timeline of the Jihad"
- Blake Ascending, p. 170, "Timeline of the Jihad"
- Grave Covenant, ch. 18
- Grave Covenant, ch. 21
- Field Manual: ComStar, p. 75
- Field Manual: ComStar, p. 75-76