We investigate sequential processes underlying the initial development of in-cloud lightning flashes in the form of initial breakdown pulses (IBPs) between 7.4–9.0 km altitudes, using a 30–250 MHz VHF interferometer. When resolved, IBPs exhibit typical stepped leader features but are notably extensive (>500 meters) and infrequent (~1 millisecond intervals). Particularly, VHF radio features indicating space stems and space leaders are identified, evidencing the conducting main leader forming. We observed five distinct phases within an IBP stepping cycle: the emergence of space stems with discrete VHF pulses at previous streamer zone edges, the conversion to a space leader, the fast VHF propagation along the space leader, an immediate transition to fast breakdown into undisturbed air, and a decaying corona fan. These measurements illustrate clearly the processes involved in the initial development of in-cloud lightning flashes and provide insights into other processes known to occur simultaneously, such as TGFs.