Arsenal’s European campaign started with a loss to Croatian top side, Dinamo Zagreb, in a game which saw French striker, Olivier Giroud sent off.
The Gunners fell behind after a Josip Pivaric shot was saved by keeper David Ospina but rebounded in off Alex Oxlade-Chamberlain.
Giroud was then red carded for a second booking when he fouled Ivo Pinto just before Junior Fernandes headed in to make it 2-0 to te home side.
Substitute Theo Walcott slotted in to give Arsenal hope but the home side held on to o extend their unbeaten run to 42 games with a first defeat of English top-flight club in the Champions League.