World No 1 Oliver Townend delivered a flying start on his 2017 Burghley champion Ballaghmor Class, scoring 23.60 to lead the field.
His fellow debut Olympian Laura Collett posted 25.80 aboard London 52 to lie fourth overnight, with Britain’s team score of 49.40 putting them in top spot ahead of Sweden and Japan.
Tom McEwen and Toledo De Kerser complete the British dressage tests on Saturday, before attention then turns to Sunday’s cross-country test at Sea Forest Park, which promises to be a critical part of the medals race.
Britain last won an eventing team gold at Munich in 1972, but they have an outstanding chance this time around, with a German team led by double Olympic individual champion Michael Jung likely to be their biggest threat.
Jung is in dressage action on Saturday, and Germany can expect to climb the leaderboard from their current position of fifth.
Huddersfield’s Townend said: “I am very happy with the horse. We know he is special, and 23.6 is a very good starting mark for the team.
“He went in and did his best in conditions that he is not used to.
“He did a very commendable job, and fingers crossed, we just keep the work up over the next three or four days and see where we end up.”
Collett, though, had a tinge of disappointment after her test, adding: “I know he can be there or thereabouts. Unfortunately, it didn’t come off today.
“He is still a very exciting horse, and he is allowed to have an off-day.”