Originally Posted by
Bercor
Tolkien struggled with the correct number of Balrogs throughout his life. An early conception, presented in the Fall of Gondolin writings and partly in the Silmarillion, there were many Balrogs but they were much less powerful than Durin's Bane, for example, and were not Maiar, but constituted a race of themselves. Tolkien, when starting to consider them powerful Maiar, eventually came to the conclusion that there couldn't have been more than 7 Balrogs. We're going with the latest concept.
The other generals will probably be Boldogs.