[2] The progress of his initial military career was not clear — but, presumably, like Ma Yin, he was initially conscripted into the army of the late Tang dynasty warlord Qin Zongquan, who controlled his home region, and then, after Qin declared himself emperor of a new state, was sent south on an expedition commanded by Qin's general Sun Ru; after Sun was defeated and killed by Yang Xingmi, Yao, presumably as was in the case with Ma, followed Liu Jianfeng, who headed southwest, eventually taking over Wu'an Circuit (武安, headquartered in modern Changsha, Hunan), where Liu became its military governor.
As Ma was then, under orders Liu previously ordered, attacking Shao Prefecture (邵州, in modern Shaoyang, Hunan), which was then occupied by the officers Jiang Xun (蔣勛) and Deng Jichong (鄧繼崇) (who had previously rebelled against Liu's rule), Zhang sent emissaries to formally summon Ma back from the Shao campaign.
Yao, who was then serving under Ma in the Shao campaign, persuaded him to accept, stating, "You, Lord, were effectively three people in the same flesh with General Liu and Commander Zhang.
Ma therefore left the officer Li Qiong (李瓊) to continue to the Shao siege while he himself returned to Wu'an's capital Tan Prefecture (in modern Changsha, Hunan) to accept command of the circuit.
[5] After the end of the campaign, Ma commissioned Yao as the prefect of Li Prefecture (澧州, in modern Changde, Hunan).
[2][6] As of 910 — by which time Tang had fallen, and Ma Yin was effective the ruler of his own state (Chu, as its prince) that formally was a vassal to Tang's successor state Later Liang — Yao Yanzhang was referred to as the prefect of Heng Prefecture (橫州, in modern Nanning, Guangxi), in addition to being the commander of the Jingjiang army.
[7] In 911, at Ma's request, the Later Liang emperor Zhu Huang commissioned Yao to be the deputy military governor of Ningyuan.