A Recruitment 'Drive' is a period or window of opportunity that you can recruit characters before the story prevents otherwise.
For years I've always wanted to know exactly when you can go out and recruit characters and when you cannot throughout the game. For my last playthrough which was 2 years ago, I made notes of every time I was able to go out and recruit characters and when I was not able to because of story related stuff. This took a lot of resetting the game and loading up various saves to test my theories. I believe I came up with a 95% accurate list, the other 5% comes from leaving out when some of the drives end..for some reason that only 'past me' knows. Generally recruitment drives "end" when you can't recruit no more characters for that period because other characters are not available per their own requirements.
Before going back to the Fort the third time.¹
- Mukumuku - the first recruitable character before having an HQ/castle.
- Rikimaru
Millie
Kinnison && Shiro
- Zamza - his first recruitment chance is missed if not recruited before toto burns.
This occurs after leaving toto to head to Muse on errand for Pilika.
Recruitment Drive begins when receiving the first assignment from Jess to spy on the highland camp for the size of provisions.
Don't forget to explore Muse to trigger the scene with Elza, if you're trying to do the mini quest involving her and Clive.
- Tuta
Anita - after the scene Leona in the tavern concerning Jess's assignment, leave the tavern and return and she'll appear.
Templeton - may need to visit toto twice after meeting him at mercenary fort.
Castle Level 1
Recruitment Drive begins when acquiring the castle after defeating Abomination.
- Oulan
Recruitment Drive begins after defeating Solon Jhee and deciding to become the leader of the army.
If you speak to Fitcher who will be wandering about near in the main walkway near the entrance of the Castle, this drive will end prematurely. This dialog is forced as it's a proximity trigger, so you will have to sneak by him via exiting the castle by taking the path through the Inn, and leaving through the opening in the wall outside.
- Richmond
Yoshino
Recruitment Drive begins after talking to Fitcher and agreeing to take him to Two-River.
- Tai Ho
Yam Koo
Taki
Hans
Tetsu
Don't go back to the Castle as this will end the drive, instead head straight to South Window.
- Clive
- Alex + Hilda
Stallion
Shilo
Adlai
Tengaar + Hix
Gabocha
Sid
Hai Yo
Wakaba
Tony
Meg + Gadget- No more recruitable characters for this round. Character count should be 54.
Recruitment Drive begins after escaping Greenhill(scene with Culgen and Seed pledging loyalty to Jowy).
Don't go back to the Castle yet.
- Jeane
Yuzu- There are no more to recruit at this point.
Recruitment Drive begins after Miklotov leaves for his solo mission.
- Humphrey
Futch
Recruitment Drive not available after Kiba is captured and then joins the SoD.
Character count 67
Recruitment Drive begins after the meeting between Sheena and Apple in the war room.
- Lebrante
Badeaux
Feather
Ayda
Sigfried
Simone
Lorelai
Mondo
Sasuke
Hoi (after you return from Toran Republic and haven't gone to the HQ.)
- Annallee
Killey
Bob (If missing one character before getting Kasumi/Valeria)
Tomo - Tsai will approach you after the meeting with Shu and others, and you return to your room.
Recruitment Drive begins after defeating Luca Blight and Nanami wants to go for a walk, either Kuskus or South Window.
- Hoi(if you missed him)
Karen: Don't talk to the two guys outside the inn yet, for this will 'pause' the drive.
Maximillian
- LChanChan
Tenkou
Raura
- Tenkou
Gentetsu
¹: Memory fails me here and I see I didn't provide good notes for myself on this one. This generally needs to be done before Kyaro is off limits for the rest of the game and that occurs when you go to fight the Mist Shade. You can get him later and before the SoD Lockout of course. This is just the absolute earliest you can get him.
²⁻³: Didn't provide good notes.
⁴: There is a long sequence of events that plays out after you complete Jess's assignment. Muse gets taken over among other things.