Is “Proposed the strategy of a surprise attack via the Ziwu Valley” true?
attested in history
According to the 'Records of the Three Kingdoms, Book of Shu, Biography of Wei Yan', Pei Songzhi's annotation quotes the 'Weilue' stating that Wei Yan once suggested leading elite troops directly out of the Ziwu Valley to attack Chang'an, but Zhuge Liang considered it too risky and did not adopt it.
Wei Yan
In official history, he was a key minister of Shu Han who guarded Hanzhong and achieved many military exploits, but in the novel, he is portrayed as a traitor with a 'rebellious bone' at the back of his head.