A Syrian girl skips rope near the Bab al-Salameh border crossing near the Syrian town of Azaz in 2012. Her family fled to escape fighting between the Syrian army and the rebels, hoping to reach safety in Turkey. Nearly four years later, thousands of Syrians displaced by the country’s civil war continue to seek safety outside of Syria. (Muhammed Muheisen/AP)

Last week, 51 State Department diplomats objected to U.S. policy toward the conflict in Syria.

When their memo, filed via the State Department’s formal dissent channel, was leaked to the media, it made the news. But there’s a long tradition of internal dissent in the U.S. government during crises involving large-scale civilian atrocities. Indeed, from the Holocaust to the 1971 massacres in Bangladesh, to the atrocities in Bosnia in the 1990s, government officials have consistently stepped forward to disagree with U.S. foreign policy.

This latest group of dissenters wants the Obama administration to change course in the Syrian conflict and launch military strikes against the Syrian government led by Bashar al-Assad. Their dissent memo cites the more than 400,000 lives already lost in the five-year conflict as well as 12 million displaced Syrians. These State Department employees argue that the United States has both a “moral rationale” and “strategic imperatives” to use all possible means to end the violence.

The large number of signatories on the dissenting memo is truly historic, but what’s equally significant is that these diplomats have now joined a long line of government dissidents during cases of mass atrocity. These 51 names, as yet unknown,  undoubtedly will someday rank alongside Henry Morgenthau Jr., Archer Blood and Marshall Harris, 20th century U.S. government officials who took a stand against U.S. policy in response to mass killings abroad.

Here’s some background on dissent in the U.S. government:

1. Henry Morgenthau and the plight of European Jews

My research on dissenters led me to Henry Morgenthau, who served as treasury secretary during Europe’s other mass refugee crisis some 70 years ago. Morgenthau led a team of Treasury officials and State Department informants who exposed State’s failure to address the refugee crisis and uncovered its efforts to actively block Jewish emigration to the United States. In a meeting with President Franklin D. Roosevelt in January of 1944, Morgenthau and his team argued for the creation of an independent government committee to help refugees escape Nazi-occupied territory. One dissenter threatened to resign if Roosevelt did not act. Ultimately, their campaign resulted in the little-known War Refugee Board, which worked with neutral governments, refugee groups and other organizations to ultimately save 200,000 Jews.

2. Archer Blood’s protest against Pakistan’s mass killings in 1971

Archer Blood was the U.S. consul general in Dacca, East Pakistan — what would later become Bangladesh. When Pakistan launched a mass killing campaign against civilians in the East in 1971, Blood and others at the Dacca consulate protested the Nixon administration for standing by the Pakistani government and doing little to stop the atrocities. A group of 20 officials serving in Dacca sent the first ever dissent cable in Foreign Service history through the newly created dissent channel, designed to allow lower-level officials to send alternative viewpoints directly to senior officials. In response to their dissenting actions, Nixon recalled Blood and removed several of his subordinates, a story recounted in detail in Gary Bass’s “The Blood Telegram.”

3. Marshall Harris and the opposition to Bosnian atrocities in the 1990s

When Serbian forces began a brutal ethnic cleansing campaign to oust Muslims and other non-Serbians in Bosnia, a group of State Department officials wrote a dissenting letter to Secretary of State Warren Christopher arguing for a tougher U.S. response to the atrocities. Bosnia Desk Officer Marshall Harris drafted the letter, and 11 other State officials with expertise related to the conflict joined his dissent. After U.S. policy still didn’t change, Harris resigned in protest in August 1993, alongside Croatia Desk Officer Steven Walker and intelligence analyst Jon Western. George Kenney, a Yugoslav desk officer, had resigned the previous year. Western later became a political scientist specializing in American foreign policy and human rights issues.

Does the dissent channel actually work?

All of these dissenters risked their careers to argue for a change in U.S. policy during ongoing atrocities against civilians abroad — many, in fact, saw their official careers suffer as a result or felt compelled to resign to send a strong message. And only the first case cited here directly resulted in an actual change in U.S. foreign policy.

Indeed, the Holocaust-era Treasury and State dissenters stand alone in having successfully shifted U.S. policy, likely because they had an ally in the treasury secretary, who also happened to be a close friend of the president.

Some historians argue that the official State Department dissent channel has been consistently ineffective over the past 40 years. The outcome for U.S. policy in Syria, and for the signatories of this latest dissent memo is yet unknown, but no matter the result of their memorandum, they have undoubtedly added another chapter to the long history of dissent in the U.S. government amid egregious human rights abuses abroad.

Amanda J. Rothschild is a research fellow at the Harvard Kennedy School’s Belfer Center for Science and International Affairs and a PhD candidate in political science at the Massachusetts Institute of Technology. Her doctoral dissertation, “‘Courage First:’ Dissent, Debate, and the Origins of US Responsiveness to Mass Killing” traces the role of dissent in U.S. foreign policy toward mass killing over the course of the 20th century.