After President Donald Trump launched a major military attack on Iran in conjunction with Israel without providing a consistent rationale and without making a public case to Congress, it seems safe to say the result will be a further erosion of public trust in the federal government.

That trust has been fragile since the early 1970s. And while some commentators point to scandals (like Watergate), political polarization, or—in Ezra Klein and Derek Thompson’s view—excessive regulation to explain why so many Americans doubt the government’s ability to fulfill its promises, nothing has done more to erode trust than war.

After President Donald Trump launched a major military attack on Iran in conjunction with Israel without providing a consistent rationale and without making a public case to Congress, it seems safe to say the result will be a further erosion of public trust in the federal government.

That trust has been fragile since the early 1970s. And while some commentators point to scandals (like Watergate), political polarization, or—in Ezra Klein and Derek Thompson’s view—excessive regulation to explain why so many Americans doubt the government’s ability to fulfill its promises, nothing has done more to erode trust than war.

Vietnam shattered the confidence that Americans had developed in the federal government during the New Deal and World War II. Its impact on public trust has endured as a reminder of the damage that mishandled military operations can inflict on the nation.

When President Lyndon Johnson intensified the war in Vietnam in 1964 and 1965, a majority of the country still felt confident about the federal government. The impact of President Franklin D. Roosevelt’s New Deal on the economy in the 1930s and the success in defeating global fascism in the 1940s had greatly boosted public confidence in what Washington could achieve. The scale and scope of the federal government had grown dramatically during that period, bringing relief to millions of Americans suffering from economic insecurity and leaving a deep imprint on almost every element of U.S. life.

For this reason, the popular two-term Republican president of the 1950s, Dwight Eisenhower, believed that any effort to dismantle Roosevelt’s legacy would be politically devastating. “Should any political party attempt to abolish social security, unemployment insurance, and eliminate labor laws and farm programs, you would not hear of that party again in our political history,” he wrote to his brother Edgar in 1954. In 1958,........

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