Background. As fire seasons in the Western US intensify and lengthen, fire managers have been grappling with increases in simultaneous, significant incidents that compete for response resources and strain capacity of the current system. Aims. To address this challenge, we explore a key research question: what precursors are associated with ignitions that evolve into incidents requiring high levels of response personnel? 

Methods. We develop statistical models linking human, fire weather and fuels related factors with cumulative and peak personnel deployed. 

Key results. Our analysis generates statistically significant models for personnel deployment based on precursors observable at the time and place of ignition. 

Conclusions. We find that significant precursors for fire suppression resource deployment are location, fire weather, canopy cover, Wildland-Urban Interface category, and history of past fire. These results align partially with, but are distinct from, results of earlier research modelling expenditures related to suppression which include precursors such as total burned area which become observable only after an incident. Implications. Understanding factors associated with both the natural system and the human system of decision-making that accompany high deployment fires supports holistic risk management given increasing simultaneity of ignitions and competition for resources for both fuel treatment and wildfire response.