under the banner of

under the banner (of) (something)

1. Identifying oneself with a particular title, slogan, etc. Before they officially formed their nonprofit as you know it today, they went under the banner "Green Jobs for Good."
2. With the stated support for or of something. This usage is always followed by "of (something)." We're holding the rally under the banner of equality and tolerance. All are welcome.
See also: banner

under the banner of

1 claiming to support a particular cause or set of ideas. 2 as part of a particular group or organization.
See also: banner, of
References in classic literature ?
Archers from the New Forest and the Forest of Bere, billmen from the pleasant country which is watered by the Stour, the Avon, and the Itchen, young cavaliers from the ancient Hampshire houses, all were pushing for Christchurch to take service under the banner of the five scarlet roses.