Ok, this will be a long answer. For our non-Irish readers, Eamon de Valera was one of the leaders of the 1916 Rising, he was President of Dáil Eireann during the revolution but opposed the Treaty in 1921. He split from the other anti-treaty groups in 1926 and founded the Fianna Fáil party. He won power in 1932 and led governments for 21 of the next 27 years. He then served in the ceremonial role of President until 1973,

There are three problems with the legacy of a dominant political figure: firstly it is so multifaceted; secondly he operated in a context so not everything that happened was his doing ; lastly, he believed in many things we now oppose but that does not make his actions wrong at the time.

Let's look over de Valera's record in different areas.

Revolutionary period 1917-23

Despite his role in 1916 he was not a military leader. He had a significant role in building up the Sinn Féin party and fund raising for the revolution. His biggest failure was his handling of the Treaty split. He did not provide clear leadership and exacerbated the split by his deviousness. This is the main reason why he proved so divisive throughout his life.

Post revolution 1924-32

De Valera's biggest achievement was the formation of Fianna Fáil. He brought republican politics back into the democratic sphere. He also formed a populist electoral coalition based on nationalism, economic protectionism and government spending on housing and health.

In government 1932-39

De Valera's great achievement in this period was the complete resetting of Ireland's constitutional status and the effective dismantling of the Treaty. He built on the previous government's work but he proceeded extremely skilfully.

On the other hand his economic policy, particularly the economic war with Britain was a failure.

A more problematic issue was his government's social conservatism. Contraceptives were the banned, divorce was made unconstitutional and restrictions on women working were tightened. It must remembered that these were popular measures. De Valera also kept a middle ground between the hardliners and a more liberal path. For example the Bishops wanted the Catholic Church made the state church, de Valera fobbed them off with a constitutional clause recognising its position as the church of the majority.

One area where he failed to make an impact was Northern Ireland. While de Valera maintained a strong republican rhetoric he neither acted against the Unionist government nor did he pursue a policy of reconciliation.

The second world war

It was probably inevitable that Ireland would be neutral in the war. De Valera deserves credit for negotiating the return of three vital ports from the British in 1938 which made neutrality possible. A policy of non belligerence with a great deal of secret help for the Allies was adopted. Probably the facade of neutrality was too convincing, especially de Valera's bizarre decision to sign the book of condolences for Hitler. This was his own decision, opposed by the cabinet and it shocked the allies.

Post war

The last fifteen years were the weakest of De Valera's leadership. He stayed in office too long and was too loyal to the generation he had brought in in 1932. The economy faced a serious crisis with high unemployment and emigration between 1945 and 1959 and the government showed neither leadership nor imagination. De Valera's health was failing (he was almost blind) and the contrast with his more dynamic successor Sean Lemass, widely considered Ireland's best Taoiseach, is instructive,

Overall then, de Valera made several outstanding contributions to Irish history. His failures were serious and it is hard to understand many of his decisions. Part of our problem with De Valera is that his vision of a conservative, Catholic, rural country with little wealth but also little inequality is almost unimaginable today but it was very popular at the time.

Sources

There are an enormous range of sources on de Valera but no really good biography. I'm just giving a few.

Tim Pat Coogan, Eamon de Valera, the man who was Ireland (1993) gives the case for the prosecution while Diarmaid Ferriter, Judging Dev (2007) offers a defence.

Michael Hopkinson, Green against Green, the Irish Civil War is good on the split.

Richard Dunphy, The making of Fianna Fáil power in Ireland (1995) is still the best study of the party.

See Ronan Fanning, "Irish Neutrality: An Historical Review" in Irish Studies in International Affairs Vol. 1, No. 3 (1982), pp. 27-38

Also his Independent Ireland is excellent on the 1930s.