赴任 and 転勤: taking up a post and changing work location
Compare a manager's or principal's arrival to take up a post with a change of work location. Preserve overlap and distinguish a future posting from a family's completed move.
Going to take up a post
赴任 (ふにん) means going to take up a post. 「父は来月から支店長として地方へ赴任する。」 identifies the father's branch-manager role and a posting to another region beginning next month.
「新しい校長が島の学校に赴任してきた。」 reports the new principal arriving to take charge at the island school. The focus is going to the place where that role is taken up.
A change of work location
転勤 (てんきん) means a job transfer or relocation. 「兄は春から北の町へ転勤する。」 describes the older brother's work location changing to a northern town in spring. It does not state employment at a new company.
「父の転勤に伴って家族全員で引っ越した。」 reports the entire family's completed move accompanying the father's transfer. The example does not make a family move necessary for every transfer.
Descriptions that can overlap
赴任 focuses on going to a workplace to take up a role; 転勤 focuses on changing work location. A move to take up a new role can be described from both perspectives.
The next-month posting and the completed family move have different timing in their examples. Do not turn the future posting into a completed event or equate a transfer with a short business trip or a change of employer.
Must going to another region as branch manager through 赴任 be a different event from 転勤?
Show the answer and why
No. 赴任 emphasizes going to take up the role, while 転勤 emphasizes a change of work location. Both perspectives can describe the same move.