Shortly after Kerrigan defeated the United Earth Directorate forces on Korhal and retreated to Tarsonis, the UED responded with a counterattack, sending a pair of slave broods to attack Kerrigan's forces.
The scientists coordinated the zerg forces, working alongside genetic engineers which were conducting experiments on passive zerg. Security guards and pyrotechnic engineers were assigned to protect the scientists. However, Kerrigan's forces triumphed, defeating the Slave Broods and killing the scientists. The formerly passive zerg then rampaged across the battlefield.