overseas trip; overseas expedition
Often used for sports teams, military units, or organized groups traveling abroad for a specific mission or competition.
The soccer team departed on an overseas tour.
Next month, I'm scheduled to go to Europe on an overseas expedition.
海外遠征 specifies an overseas destination, while 遠征 alone can be domestic or international.
海外旅行 is a general overseas trip for leisure; 海外遠征 implies a mission, competition, or organized group activity.
Compound of 海外 (overseas) and 遠征 (expedition, campaign).