Over the fence comes first
The herd and the newcomer should know each other's smell, voice and ranking ambitions before they share ground. A few days in a paddock or stable arrangement where they can meet along a fence line lets the dramatic part — the sniffing, squealing and striking at air — happen with a barrier collecting the consequences. Watch who he befriends through the fence and who he argues with: the horse he grazes beside peacefully is your candidate for the first real introduction, and the one he fights through a fence should be met later, in company, not first and alone.
First contact: one steady horse and room to escape
Choose a field or arena big enough that a chased horse can always keep moving, with no dead corners, gateways or trough pinch-points where he can be trapped. Introduce him to the single steadiest member of the herd — ideally the one he already likes through the fence — and let them settle for as long as it takes, which is usually minutes of drama and then grazing at a distance. A companion who is calm but socially fluent teaches the newcomer the herd's rules far better than either a bully or another nervous horse would.
Build the group in layers
With the first pairing peaceful over a couple of sessions, add the rest gradually — one or two horses at a time, bringing in the herd's more dominant members only once the newcomer has allies. Releasing a stranger to a full established herd in one go invites the whole group to chase at once, which is when injuries happen. Spread the introductions across days if the yard's routine allows; each calm session banks confidence for the next, and a horse who has joined in layers usually holds a settled place in the order before long.
Food, timing and knowing when to intervene
Introduce on full stomachs, never into the excitement of a morning turnout onto an empty field, and put hay out in piles spread widely — one more pile than horses — so nobody has to challenge anybody to eat. Expect squeals, threats and a short gallop; intervene when the behaviour stops being negotiation: one horse chased relentlessly, cornered, kicked at repeatedly, or too frightened to settle and graze. Removing the newcomer for the day and retrying smaller is a successful outcome, not a failed one — forcing the timetable is how field injuries happen. Many yards also take hind shoes off for introduction periods, so ask about the yard's practice before the first session.
The quiet week after
A settled introduction is the beginning, not the end. In the first week, watch the subtle ledger: is he getting to the water and the shelter, is he holding his condition, is he always grazing at the group's edge or being moved off every pile? Small scrapes are normal currency, but a horse who is consistently excluded from forage needs the yard to adjust the grouping, the field or the feeding arrangement. Most introductions that start slowly end completely — the newcomer simply becomes a horse who lives there.
While it unfolds, KinsLe Messenger keeps every update from the yard — the manager's notes, the groom's photos of the first shared grazing — in his single per-pet hub, so you are not piecing his first week together from three people's separate messages.