紙上談兵

1. • lit. military tactics on paper (idiom)
2. • fig. theoretical discussion that is worse than useless in practice
3. • armchair strategist
4. • idle theorizing
5. • cf Zhao Kuo 赵括 zhàokuò leading an army of 400,000 to total annihilation at battle of Changping 长平之战 chángpíngzhīzhàn in 260 BC

Character by character

• 紙(zhǐ)paper
• 上(shàng)up
• 談(tán)surname Tan
• 兵(bīng)soldiers