Hold on, the 7th column? I understand the 5th column, the saboteurs. But we skipped right over to the 7th? What was the sixth? Random House:
1. the persons residing in a country at war who are devoted to aiding the fifth column in its activities, especially by lowering morale, spreading rumors, etc.
2. the persons residing in a country at war who are devoted to blocking the efforts of the fifth column.
Well, that really clears it up.