He went on to be British Commissioner with the Turkish Army providing advice to General Omar Pasha during the Crimean War.

[2] He was then deployed to Canada where he carried out survey work on the disputed border with the United States of America.

[2] Returning to the United Kingdom in 1845, Simmons became an instructor at the Royal Military Academy, Woolwich with promotion to second captain on 9 November 1846.

The British Ambassador, Lord Stratford de Redcliffe, took up Simmons' offer of his services, requesting that he report on Turkish defences and their ability to resist a Russian advance.

[2] Promoted to captain on 17 February 1854,[5] he became British Commissioner with the Turkish Army providing advice to General Omar Pasha as the Crimean War started.

[16] After he retired in September 1888,[17] the Foreign Office continued to utilise his services and in 1889 he went to Rome as Envoy Extraordinary and Minister Plenipotentiary to Pope Leo XIII.