Dabei brauchte er doch Verbündete, und ...
Without any further context to judge its meaning, is "Dabei" at the beginning of a sentence usually understood as:
He would need allies with that / in this situation, though. (with the meaning of "though" coming only from "doch")
Or:
However, he would need allies, though. (with both "Dabei" and "doch" meaning "but / however")
When "Dabei" is used with the verb "brauchen", is the first meaning more likely?