The 3rd season of DFA is known to take place in the year 3049. To understand the situation you just need a few tidbits of info. First, have a look at the inner sphere.
In season 2 we were in the “South” of the inner sphere where the “civilized” portion of the periphery are located. The “North” side is where the bandit kingdoms are. These are authoritarian and anarchic regions inhabited by criminals and mercenaries who kill, steal and commit atrocities. They regularly attack House Steiner, House Kurita, The Free Rasalhague Republic, and other periphery planets to take what they want, including slaves and material. Mercenary contracts are plentiful in this region of space.
The year 3049 is the year the Clans invade the inner sphere. They are the genetically engineered, and socially indoctrinated descendants of the Star League Defense Force who left the Inner Sphere to find a new destiny. Their destiny was one of hardship, survivalism, murder, constant war and, and finally modification of their own genetics to breed a better human. They intend to overthrow and subjugate the Inner Sphere and its Noble Houses in order to impose their way of life and an idealized version of the Star League on its inhabitants. They begin this by first invading the bandit kingdoms and mostly wiping them out to the last man, woman and child; they consider pirates to be less than human. Some are captured and used as Bondsman, an analogue to modern indentured servitude via the court. The month of August was mentioned, and this means the invasion has just begun, with devastating results.
About the Clans:
Clan society falls into Military and Civilian castes, with sub castes according to a person’s role in society. Some clans allow limited movement between castes, most do not. The Military castes essentially rule society and all decisions are made, argued and prosecuted via combat, challenge or personal violence. Most Clan warriors don’t live past 40. Being genetically engineered they are stronger, faster and better shots than their inner sphere counterparts. Their technology is also more advanced than the Inner Sphere, essentially making a single clan heavy mech a match for 2 Inner Sphere heavies or 3 mediums. The military caste is mostly bred in a laboratory setting. Natural procreation is frowned upon and considered disgusting by the military caste. The discussion of it has been known to make Clan warriors sick to their stomach. Civilian castes have no such hang-up. The Military caste also speaks a specific form of English where contractions are not used, as they feel that contractions are a bastardization of the language.
When first encountered, the Clans use of encrypted battlespeak during combat, hyper-advanced weaponry, and strange customs lead many to believe them to be a hostile race of aliens, and not humans. Inner Sphere computers also went haywire attempting to identify hostile mechs, leading to the infamous moment when the clan mech called a Timberwolf was named the “Mad Cat” by Inner Sphere combatants as their computer kept switching ID between “MAD-3R” and “Catapult” when it was targeted. Clan warriors practice “Zellbrigen,” a formal methodology of honorable battlefield conduct that focuses on single combat between warriors.