streaming replication and WAL

Hi,
let's suppose I have:
  - a primary server with its own local archive location, configured for
continuous archiving
  - a standby server without archive.
These servers are configured for Sync streaming replication .
Let's suppose that the standby stays down for a long time, then it
restarts, goes into catchup mode and now needs some old WALs from the
server archive location.
Will the standby be able to automatically drain those files through the
replication or only the WALs being currently updated by the primary ?

Regards
Pupillo