Many mortal humans have an impression of celestial warfare comprised entirely of apocalyptic scenes offered by Hebrew, Enochian, & Judeo-Christian texts, of endless war-ravaged wastelands and nigh-infinite armies of titanic celestial warriors, locked in eternal conflict. Such planes do exist, certainly, and most celestials have seen- or will see- them at some time, they are in fact more an exception than a rule in this cosmic war. (It is interesting to speculate how any mortal might have witnessed such a realm and lived to tell the tale, though!)
The vast majority of the war more closely resembles a Machiavellian court, with strong overtones (and undercurrents) of the Cold War of Earth's 20th century. Celestials are eternal, and their battles can smolder for generations, their maneuvers political, their strategies epic and insidious. The terrestrial realms are a convoluted chessboard of complex micro-actions, the subraces and mortals themselves merely pawns and pieces nudged, mostly unwittingly, toward some ever-evolving end-game which lies beyond an infinite horizon.
This very complexity in itself is, among the celestial factions, a badge of honor and prowess, although some with less experience in the war will occasionally make an effort to sweep the pieces aside, or overturn the board, with consequences usually most catastrophic to themselves and their reputations, and occasionally, to the mortal pawns in their wake.
In addition to the planar battlefields and the war of subtlety, there are indeed occasional bloody skirmishes, though because advancement in such ranks is slow as the growth of whole forests, the true warlords and generals know one anothers' defenses and tactics too well. Most such skirmishes occur in the lower ranks of the factions, and are in fact, as often internal as engaged with an enemy. This is no less true among angelic troops than demonic, although truthfully, angelics are more often the aggressors when skirmishes cross faction lines.
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