From 《左传·僖公二十八年》: 险阻艰难备尝之矣 — 'every danger and hardship had been tasted to the full.' Originally said of Duke Wen of Jin, who endured 19 years of exile before becoming ruler.
memory
Four synonymous characters piled together for emphasis: 艰 (hard) + 难 (difficult) + 险 (dangerous) + 阻 (obstructing). Each doubles the force of the next.
