A graduate of the Royal Military College, Duntroon, Cosgrove fought in the Vietnam War, receiving the Military Cross in 1971. From 1983 to 1984, he was commander of the 1st Battalion, Royal Australian Regiment (1 RAR), and he later served as commander of the 6th Brigade and the 1st Division. Cosgrove rose to prominence in 1999, when he served as commander of the International Force for East Timor (INTERFET), which oversaw the peacekeeping mission in East Timor during its transition to independence.
Cosgrove was Australia's Chief of Army from 2000 to 2002, and then Chief of the Defence Force from 2002 to 2005, receiving corresponding promotions to lieutenant general and general. Cosgrove retired from active service following the end of his term as Chief of the Defence Force, and subsequently served as leader of a taskforce helping to rebuild communities in Queensland after Cyclone Larry in 2006. In January 2014, Cosgrove was named to succeed Dame Quentin Bryce as Governor-General of Australia. He was sworn in on 28 March 2014, and created a Knight of the Order of Australia on the same date.
Cosgrove was born in Sydney, New South Wales, on 28 July 1947. He was educated at Waverley College in Sydney, then followed his father, a warrant officer, into the Australian Army by attending the Royal Military College, Duntroon in 1965. Cosgrove's uncle, Bill Cosgrove, was a professional Australian rules football player, but was killed in action whilst serving with the Royal Australian Air Force during World War II.
Lieutenant Peter Cosgrove was commissioned on 11 December 1968 and was allotted to the Royal Australian Infantry. He arrived in Vietnam on 3 August 1969 and was posted to 9th Battalion, The Royal Australian Regiment on 20 August 1969. On 10 October 1969, Lieutenant Cosgrove was commanding 5 Platoon, B Company. The platoon located an occupied bunker system in an area where, because of the proximity of allied troops, indirect fire support was difficult to obtain. In spite of this, he led his platoon in an assault on the bunkers without indirect fire support, capturing the system and killing and wounding at least four enemy without sustaining any casualties. On 16 October 1969, 5 Platoon located another bunker system occupied by about a platoon of enemy. Lieutenant Cosgrove silently deployed his own platoon for an attack. His assault completely surprised the enemy causing them to flee, abandoning large quantities of food, stores and documents. The following day in the same bunker system a party of enemy approached his right forward section and was engaged by the sentry. Knowing that the remainder of the section was elsewhere on other tasks, Lieutenant Cosgrove ran to the contact area and personally conducted the fight against the enemy. As a result of his actions, two enemy were killed and three weapons and four packs containing rice were captured. He was awarded the Military Cross for these actions. In 1980 he was awarded the National Medal. In the mid-1980s he commanded the 1st Battalion, Royal Australian Regiment.
Cosgrove came to national fame in 1999 when, as a major general, he led the international forces (INTERFET) in a peacekeeping mission to East Timor. The mission's success made him one of Australia's most respected and popular military leaders. He was promoted in 2000 to lieutenant general as Chief of the Army and in 2002 to general as Chief of the Defence Force.
In 2004, the Foreign Minister Alexander Downer queried the judgement of Federal Police Commissioner Mick Keelty. Following a joint interview with the then Defence Minister Robert Hill, Cosgrove was accused of "playing politics" when he said that, on this occasion, he disagreed with Keelty's point of view. However, Cosgrove expressed strong support for the Police Commissioner in his Australian best selling autobiography, My Story, published in 2006. On 3 July 2005, Cosgrove's three-year appointment as Chief of the Defence Force was completed, and he was succeeded by then-Chief of Air Force Air Marshal Angus Houston.
On 23 March 2006, Cosgrove was selected to lead the Queensland Government taskforce of rebuilding communities damaged by Cyclone Larry, a Category 5 tropical cyclone that devastated the Innisfail region of northern Queensland. "In recognition of the important contribution General Cosgrove made to the community of North Queensland following Cyclone Larry", on 11 October 2008, Queensland Premier Anna Bligh announced that a new residential suburb in the Bohle Plains area of Townsville would be named Cosgrove.
Cosgrove served on the board of Australia's main airline Qantas between July 2005 and January 2014 and is on numerous other boards as chairman or member. He served as Chancellor of the Australian Catholic University between November 2010 and January 2014; and is Honorary Patron in Chief of the ACT Veterans Rugby Club and the Rosies Youth Mission. Peter Cosgrove was appointed as Patron to the Australian Volunteer Coast Guard Association in 2015.
On 28 January 2014, Prime Minister Tony Abbott announced that the Queen had accepted his advice to appoint Peter Cosgrove as the next Governor-General of Australia, to succeed Quentin Bryce in late March. On 25 March, Abbott announced that the Queen had also approved the reinstatement of the grade of Knight or Dame in the Order of Australia (she had abolished it in 1986 on the advice of Bob Hawke), and that the Governor-General would be ex officio the Principal Knight or Dame of the Order. The incumbent, Quentin Bryce, was immediately made the first new Dame of the Order. On 28 March Cosgrove succeeded Dame Quentin and was sworn in as Governor-General by Chief Justice Robert French, becoming Sir Peter Cosgrove.
Cosgrove married Lynne Payne in 1976; they have three sons (Stephen, Philip and David) and one grandson, and lived in Sydney before taking up residence in Government House, Canberra. Cosgrove is a Roman Catholic and frequently attends Mass in the St Christopher's Cathedral parish in Canberra.
Sir Peter is a strong supporter and member of the Sydney Roosters. He is also a keen follower of cricket and rugby union.
Cosgrove's full title: His Excellency General the Honourable Sir Peter John Cosgrove, Principal Knight and Chancellor of the Order of Australia, Military Cross, Governor-General of the Commonwealth of Australia. 2014–present: Colonel-in-Chief of the Royal Australian Army Medical Corps
2014–present: Colonel of the Regiment of the Royal Australian Regiment
Victoria:2016 Doctor of Laws (honoris causa), Monash University
the suburb of Cosgrove in the City of Townsville, Queensland