Robert Greening joined the Australasian Squadron of the Royal Navy in 1906 as a Boy 2nd Class. He served on the armoured cruiser HMS Powerful before going to the United Kingdom in 1909 as an Able Seaman to undertake specialist torpedo training in HMS Excellent. Afterwards he was posted to serve in several battleships, culminating in 1912 with his posting to the battle-cruiser HMS New Zealand in which he visited her name country in 1913. He later transferred to the cruiser HMS Pyramus on the Australasian Squadron, taking part in operations such as escorting the New Zealand occupation force to Samoa and the Expeditionary Force to Egypt, as well as blockading actions against the German cruiser Konigsberg of East Africa. In 1916 he volunteered to join the submarine service, serving in several before being promoted to Warrant officer in 1918. He served in the New Zealand Division of the Royal Navy for three years on the cruiser HMS Chatham and the depot ship HMS Philomel. He then reverted back to the Royal Navy, serving again in submarines until he transferred permanently to the New Zealand Division in 1935. He then served at the shore base HMS Philomel until retiring in 1940. However, he almost immediately rejoined the Navy being involved in the equipping of defensively armed merchant ships and the armed merchant cruiser HMS Monowai. Later, he was involved in the setting up of the Navy's mine warfare organisation, laying minefields and disposal of any mines washed ashore. In 1941 he was created a Member of the Most Excellent Order of the British Empire by the New Zealand Government. In 1942 he was appointed in charge of the Defensively Equipped Merchant Ship Organisation.
- Officer of the Most Excellent Order of the British Empire - Was established by King George V in June 1917 for services to the British Empire. In December 1918 the Order was split into two divisions: Civil division for civilian recipients; and a military division for distinguished service in action. The insignia of the award from both divisions is identical, distinguished only by their ribbons. The rose-gray ribbon with narrow pearl grey stripes shows it was awarded from 1936 onward under the military division of the award.
- 1914-15 Star - Awarded to servicemen and servicewomen who served between 5 August 1914 and 31 December 1915 in any "theatre of war", provided they had not qualified for the 1914 Star. Those eligible for the medal must have 'served on the establishment of a unit in a theatre of war' during the relevant dates of operations in that area. This included service in Gallipoli (25 April 1915 - 31 December 1915), Egypt (5 November 1914 - 31 December 1915) and service during the capture of German Samoa on 29 August 1914.
- British War Medal - Recognises the successful conclusion of the First World War. Its coverage was later extended to recognise service until 1920, recognising mine clearing operations at sea, and participation in operations in North and South Russia, the eastern Baltic, Siberia, the Black Sea and the Caspian.
- Victory Medal - Was issued to all those who had already qualified for the 1914 Star or the 1914-15 Star, and to most persons who had already qualified for the British War Medal. It was awarded to all New Zealand troops serving overseas, except for those who arrived in Samoa after 30 August 1914 and those serving in Great Britain only. It is also sometimes referred to as the "Allied War Medal", because the same basic design and double rainbow ribbon were adopted by 13 other allied nations.
- The Defence Medal - Awarded to British military and civilian personnel for a range of service in the United Kingdom, and to British, British Commonwealth and British Colonial personnel who served outside their home countries in a non-operational area or in an area subject to threat such as air attack. The centre of the ribbon is flame coloured, and the edges are green, symbols of the enemy attacks on Great Britain. Two black stripes represent the blackout in Great Britain.
- War Medal - Awarded across the British Commonwealth to all fulltime members of the Armed Force for 28 days service between 3 September 1939 and 2 September 1945 irrespective of where they were serving. On one side is an effigy of King George VI. On the reverse is a lion trampling on a dragon symbolising the Axis powers. The ribbon is the red, white and blue of the (British) Union Flag.
- Coronation Medal 1911 - Issued to celebrate the coronation of King George V in 1911. This was the first occasion that the medal might be awarded to those not actually present at the ceremony itself.
- Coronation Medal 1937 - Issued to celebrate the Coronation of King George VI in 1937. It was awarded in large numbers to citizens of the British Commonwealth including New Zealanders both military and civilian.