There were many underground espionage activities during the War of Resistance.
Tips
history
特务 carries strong negative connotations in Chinese due to its association with the KMT's secret police (军统/中统) and Japanese spies during WWII. In Chinese war films, 特务 is almost always the villain.
usage
特务 implies covert, hostile intelligence work. For neutral/friendly spies, 特工 (tègōng, special agent) or 间谍 (jiàndié, spy) are used instead. 特务 is the most emotionally loaded of the three.
