'War chest' is a common English idiom for funds that are put aside for political or business 'battles' -- usually for things like election years, lobbying, protection against hostile takeovers, and so on.
The term appears to have come into use in the mid-1800s, although it is often said to have originated from literal chests of money hoarded by medieval warlords to pay and outfit warriors, or alternatively, chests used to hold weapons and armor for war. The former was more likely to be referred to as a coffer; the later, as far as I can find, simply a 'chest'. Its appearances in written works use it primarily, and originally, in the metaphorical sense rather than refering to a piece of furniture.
In business, the more pleasing term 'cash mountain' may sometimes be used.