The phrase "an open battleground" is correct and usable in written English.
It can be used to describe a situation or environment that is competitive, contentious, or where opposing sides are actively engaged in conflict.
Example: "The debate over climate change has become an open battleground for scientists, politicians, and activists alike."
Alternatives: "a free-for-all" or "a contested arena".
During the nine-year tenure of President Mikheil Saakashvili, the pop charts have been an open battleground between those loyal to him and his policies, and his intractable foes.
These battles were, in a sense, an introvert war fought by the city's occupants who turned their own homes into an open battleground – a war fought from alley to alley, building to building.
He was assigned to the tough Western District, then the wide-open battleground of drug dealers.
It straddles Yesler Way, long a nexus for all things sinful and battleground between proponents of an "open town" and those hoping to suppress vice.
There is a battleground open to players level 85 or higher called the Battle for Gilneas.
The question of whether the race spills over into the convention has opened a new battleground among campaigns in the complicated system of allocating delegates in state and county party gatherings that follow the primaries and caucuses.
Instead we have a whole new battleground opening up online where boys can attack, humiliate, belittle us and do everything in their power to destroy our confidence before we even leave high school.
BT's pending £12.5bn acquisition of the UK's largest mobile operator, EE, which is awaiting regulatory approval, would open up a further battleground between the two companies as Sky also offers mobile contracts via O2.
Terrorist attacks in Israel and India have threatened to open new battlegrounds from the Palestinian territories to Kashmir that could unravel the coalition.
After years of fighting organized labor in state houses and on Capitol Hill, conservatives opened up a fresh battleground in Kentucky last month, pushing a brand new crop of anti-union laws in counties across the state.
People with eating disorders like anorexia have opened up a new battleground in the insurance wars, testing the boundaries of laws mandating equivalent coverage for mental illnesses.
