The phrase "a key for battle" is correct and usable in written English.
It can be used in contexts discussing strategies, tools, or methods that are essential for success in a conflict or competition.
Example: "The general believed that having a well-trained army was a key for battle in achieving victory."
Alternatives: "a crucial element for conflict" or "an essential tool for warfare".
With the UK's persistent budget deficit already a key battle ground for the May 2015 election, the minutes provide support for Labour's argument that the deterioration in the public finances was justified by the need to rescue the banks.
Armed with open source for a key battle Getting data quickly has been a key battle in the fight against Ebola, which has caused more than 3,000 confirmed deaths in Sierra Leone since May 2014, according to the National Ebola Response Centre.
The future of the National Health Service is a key battle ground for the election, with Ed Miliband putting it front and centre of his campaign so it was strange the Chancellor didn't repeat his typical line that the NHS can only prosper in a strong economy.
"They've got a lot of big players in the pack, a lot of big, strong guys but as well as that they are very well drilled in the forward elements of the game – their scrum is very good and their maul is good as well, so it's a key battle area for us.
Clemson and Florida State meet in a key A.C.C. battle.
Here George Washington and his Continental Army faced British General William Howe in the Sept. 11, 1777, Battle of the Brandywine — a key battle of the war and a stinging defeat for the Americans.
Though sports have always been a key site for wider ideological battles over what it means to be American, few presidents have inserted themselves into disputes within and about sports as directly as Trump has.
Sitting opposite is Dora Challingsworth, another retired shop steward who was a key figure in the battle for women's rights at Ford.
