Watch: Walcott scores to start long road back for Arsenal vs. Bayern Munich

Arsenal entered the second leg of the Champions League round of 16 with a nearly impossible task, but Theo Walcott got the Gunners started on the right foot against Bayern Munich.

Trailing 5-1 on aggregate after a collapse in Germany in the first leg, Arsenal struck first in the second leg, with Walcott beating Manuel Neuer with a clinical, powerful finish in the 20th minute.

Arsenal, which is facing a seventh straight elimination in the round of 16, has plenty of work to do and must do it without Danny Welbeck, who pulled up lame in pregame warmups and was pulled from the starting lineup.

Arsenal would go through to the quarterfinals with three more goals, all while keeping Bayern Munich scoreless.