龟虽寿

Written around 207, after 曹操's campaign in the north against the Wuhuan, as the last part of the suite 步出夏门行. It opens 神龟虽寿，犹有竟时 'though the sacred tortoise lives long, its days still come to an end', and its centre is 老骥伏枥，志在千里。烈士暮年，壮心不已。 'The old steed in the stable still longs to run a thousand li; the hero in his last years keeps his high ambition.'

烈士 here is a man of high ambition. Today the word means a martyr, someone who died for a cause.