Born in rural Northland, Coates grew up on a farm, which he took charge of at a young age due to his father's mental illness, before becoming a member of Parliament in 1911.

Born at Ruatuna,[1] the family home on their sheep and cattle farm at Hukatere in the Matakohe district[2] on the Kaipara Harbour, New Zealand, Coates took on significant responsibility at a relatively early age because his father suffered from bipolar disorder.

In the 1911 parliamentary election, Coates won the Kaipara seat, having stood as an independent candidate aligned with the Liberal Party.

In Parliament he generally voted with the Liberals, and formed part of the group that allowed Joseph Ward to keep his position as prime minister.

At the outbreak of World War I, Coates attempted to enlist for active service, but the prime minister, William Massey, dissuaded him from doing so by – the Reform Party had only a tenuous majority.

In November 1916, however, Coates finally gained permission to join up – he served with considerable distinction, winning a Military Cross and bar.

When Massey died on 10 May 1925, Sir Francis Bell became caretaker prime minister while the Reform Party could make a decision on it long-term leadership.

[12] Reform's slogans were also about its leader such as 'Coates and confidence', 'Coates and certainties' and 'coats of with Coates' which were aggressively advertised in newspapers to convey safety and decisiveness.

[13] Personally, Coates was not ideologically committed any particular political or economic philosophy more noted for his good sense and pragmatism.

It spoke of Reform promising government stability, economic security, equal opportunities and New Zealand's role in imperial defence.

"[15] He defended freehold land policy from Labour Party attacks and even promised to introduce a contributary insurance scheme to fund payments for the invalided and unemployed.

[16] The sheer scale of his victory would later turn into a difficulty of its own as Coates found it difficult to live up to the high expectations on him.

[18] Coates responded by pushing through emergency legislation empowering local authorities to borrow funds to create jobs.

[21] Coates had a temporary reprieve from domestic troubles when he left to lead the New Zealand contingent to attend the 1926 Imperial Conference in London.

He met with Canadian Prime Minister William Lyon Mackenzie King, US Secretary of State Frank B. Kellogg and President Calvin Coolidge mostly discussing matters of the South Pacific.

[29] Rural areas, usually Reform's stronghold, were deeply dissatisfied with the government and had the opportunity to make their dissatisfaction known at the Raglan by-election in September 1927.

[30] Even Reform friendly papers acknowledged popularity for Coates and his government had collapsed since 1925, though he still was able to attract crowds when he visited the electorate during the campaign.

[31] Coates premiership was marked by an intention to develop the rural economy of New Zealand, from which he stemmed, particularly in terms of roads and transport infrastructure.

[33] As the Great Depression loomed and New Zealand's economy began to further deteriorate, Coates and the Reform Party attracted considerable criticism.

[39] In 1931, the Labour Party completely withdrew its support from the United government, protesting about various economic measures which it regarded as hostile to workers.

Coates and the Reform Party subsequently agreed to form a coalition with United, preventing a general election in which Labour might have made significant gains.

[40] United's leader, George Forbes, remained prime minister, but Coates and his Reform Party colleagues gained a number of significant posts.

[41] In the 1935 general election the coalition suffered a major defeat, winning only 19 seats: Coates nearly lost Kaipara.

The Labour Party, which had won 53 seats, formed its first government and Michael Joseph Savage became prime minister.

He experienced a period of financial difficulty resulting from the sudden loss of income, but his situation improved when a group of friends presented him with a large sum of £550 as thanks for his long service.

Eventually Coates preferred choice Adam Hamilton, a former Reform member, won the leadership ballot by one vote.

In the house Coates was critical of Labour's finance minister Walter Nash, arguing the government's new regulations would restrict competition, inflate costs and slow economic growth.

Coates strongly believed partisanship was a misplaced approach during war, and attempted to convince both Labour and National to work together.

Coates and Hamilton openly criticised this decision, and the day after their resignation became effective,[47] they rejoined the War Cabinet on the invitation of the prime Minister, Peter Fraser.

[3] In the face of British decline during the war, Coates encouraged Fraser to develop closer strategic relationships with the United States instead.