The Borg do everything as a whole, and in a culture where the individual is irrelevant sacrifices are readily made. The Borg fight in exactly that way. When a new race is encountered by the Borg they are probed, if deemed worthy the Borg will attempt to assimilate them. If the attempt fails, and their ship is destroyed then another ship is sent to take over for the lost vessel. If that ship is destroyed then another will be sent, and another, and another, until the target species is eventually worn down and finally assimilated into the collective.     Borg drones are used exactly as the ships are. A borg will walk into a hostile situation and be the first to be attacked, then the next drone will do the same, any decent weapon will drop at least two drones and then the Borg will have had a chance to adapt the drones' personal shields - making the attack ineffective.

When in a new - unscouted - environment, the Borg assault drones need a separate drone to assess large numbers of threats for them. This drone - known as a Multiplexor drone - is able to target the most immediate threats and direct the assault drones accordingly.     The following diagram displays this: