I attempted to send a Double Agent alone against an enemy sub carrying 142 drillers (no specialists). When they engaged in combat, the enemy drillers were not killed. The result was all of the drillers were still intact, but my double still defected. From my understanding, the enemy drillers should have been destroyed.
Additional Note: The Double Agent was not originally mine, it was used against me and then defected to my side. The person who used the agent against me was NOT the same as the one that attacked me with the 142 drillers (pink).
Screenshots of what happened:
http://imgur.com/a/ITCpN