In spite of exhortations from Tecumseh Procter had already abandoned Amherstburg and Detroit and began to retreat up the Thames River on 27 September .
Tecumseh led the confederation of Indian tribes allied to Britain .
In spite of exhortations from Tecumseh , who led the confederation of Indian tribes allied to Britain , Procter had already abandoned Amherstburg and Detroit and began to retreat up the Thames River on 27 September .