Complex sentence: Instead, private individuals would rely upon their slaves or supporters to take action, not only forming bucket brigades or attempting to smother smaller fires but also demolishing or razing nearby buildings to slow the spread of the fire.
Split into simpler sentences: Instead, private individuals would rely upon their slaves or supporters to take action. They would not only form bucket brigades or attempt to smother smaller fires, but would also demolish or raze nearby buildings to slow the spread of the fire.