In July 1943, Allen took part in the Battle of Mount Tambu where he rescued twelve United States soldiers who had been wounded in the fighting.

[1] He rejoined his battalion in time for the Syria–Lebanon Campaign where he attended to casualties all night under fire on 10–11 July 1941 near Khalde and walked for 10 km the next morning to get transport.

[1] After serving in Ceylon (now Sri Lanka) Allen's battalion returned to Australia in August 1942, then in October sailing for Papua.

[1] Allen rescued wounded soldiers under fire around Crystal Creek on the 7 and 8 February 1943 for which he was awarded the Military Medal.

[1] — the citation stating: ‘Private Allen’s bearing and his untiring efforts in tending the wounded and helping with rations and stores were an inspiration’.

Swedish power metal band Sabaton wrote the song "The Ballad Of Bull" about Allen for their 2014 album Heroes.