Shal'annu

Shal'annu is a formalized system of rules and conduct that governs warfare between most Sangheili clans and fiefdoms. Derived from an archaic Sangheili dialect term roughly translated as "strife with concealed blades", Shal'annu is typically conducted via assassins and other covert means, though may at times escalate over into open warfare between houses. Originally conceived to limit outside casualties, Shal'annu is now a highly ritualized affair rife with tradition, and is heavily regulated by various strictures and pacts. Shal'annu most notably regulates the acceptable use of force in a conflict. For example, tactical glassing is strongly frowned upon to the point of being regarded as a grave dishonor while strategic glassing is banned, and even most open warfare is fought by infantry and light vehicles at best. Indeed, the less force a house can bring to bear and still defeat their opponents, the more honorable they will be seen as. As such, most Shal'annu conflict is unseen despite being ubiquitous.

Should a participant break the rules of Shal'annu, such as by using weapons or tactics deemed too destructive or barbaric, it is part of the contract that other clans (as opposed to the ministries) discipline the offending clan. Depending on how severely the rules were broken, the offending house may merely face reproach and disgrace in the eyes of the other clans. This is already a powerful form of peer pressure, as status and honor are key to Sangheili politics. A clan with a stained reputation will find few friends in a time of need, and even otherwise they may be cut off from otherwise lucrative dealings. More severe breaches may be met with formal excommunication or removal of nobility status, and in extreme cases (such as the use of strategic glassing) a house may be entirely eliminated and stricken from records. Since all major houses are aware of the rules, such cases are extremely rare. Lesser infractions or borderline cases will merely tarnish the offenders' reputation and honor. Though the rules of Shal'annu extend to the non-Sangheili subjects of a fiefdom, they do not apply outside inter-house warfare (such as actions against alien species, or under the Covenant, groups deemed to be apostates or heretics).

The binding rules of Shal'annu have lapsed several times in Covenant history. Most recently, the Feudal Period saw many marcher polities engaged in uncontrolled mass warfare. The Second Illumination saw the ancient contracts reviewed and renewed. Even then, however, an important part of the contract between the Sangheili and San'Shyuum has always been the delicate balance of power between the two, with the Prophets always careful not to step onto what was definitively seen as the Sangheili's cultural and political territory. This meant that the pacts were always re-negotiated between the Sangheili nobles themselves rather than being handed down by the Prophets.