Alexandre Lacazette was sent off as Arsenal slumped to a disappointing first-leg defeat against Bate Borisov in the Europa League last 32.
Stanislav Dragun nodded home Igor Stasevich’s free-kick for the game’s only goal just before half-time.
Lacazette had a goal disallowed early in the second half before being sent off for elbowing Aleksandar Filipovic.
A resolute Bate held on for the win, their first over an English side at home in European competition.
The Belarusian champions will now take a slender lead to Emirates Stadium for the second leg next Thursday.
It was no more than Bate deserved as Arsenal faded quickly after a bright start on a bumpy pitch and sub-zero conditions in Belarus.
Aliaksei Baga’s side were playing their first competitive match since December and doggedly held on to their lead in the second half.
Arsenal, in contrast, managed just three shots on target despite enjoying nearly 77% possession.