The phrase "a battle outside" is correct and usable in written English.
It can be used to describe a conflict or struggle occurring in an external location, often in a metaphorical or literal sense.
Example: "As the storm raged on, I could hear the sounds of a battle outside, echoing through the walls of the old house."
Alternatives: "a conflict outdoors" or "a fight beyond".
There's a battle outside and it's raging.
During a battle outside Mexico City, Pierce's horse fell on him.
On Saturday, as I reported, the founder of a Libyan online broadcaster, Mohammed Nabbous, was killed by gunfire while reporting from a battle outside Benghazi.
The civil war that followed ended in a battle outside Verona.
Hastening to relieve the city, al-Djarrah was defeated and killed, and his army practically annihilated in a battle outside the city on 9 December 730.
Flamininus therefore led his force of 50,000 men to Sparta and, after defeating the Spartans in a battle outside the city, began investing the city.
And even if they wanted to, a raging gun battle outside would probably prevent them from getting very far.
In a wild, half-hour battle outside, four of the attackers were fatally shot and a fifth, who had explosives strapped to his body, was blown up on the main steps of the grand sandstone building.
"This is a corrupt, undemocratic police state, but what is going on is not a war in Syria but a battle by outside players for Syria," he said in an August interview in an office at the Writers Union building in Amman.
He eventually summoned me in and said his only comment was that the scene when the characters sit down to have a grand dinner party in the railway carriage while a battle rages outside was completely wrong: the family would never have had napkin rings.
Israeli forces shot and killed a Hamas militant in the West Bank city of Jenin today in a gun battle outside a fire station in which a bystander was also killed.
