Just over a month ago, the Iraqi scholar and historian Hisham al-Hashimi was murdered in Baghdad. His killers, two of them, arrived on a motorbike and did not hang around. They are yet to be identified.

Al-Hashimi’s death was a shock and an aberration, but not because of its gangland character; instead because of who he was. Many involved with politics and protest have been murdered lately in Iraq, but few like al-Hashimi. Gregarious and well-liked, he had many friends, and his work was read and cited across the world. A sometime critic of the failures of the state, he was nonetheless close to many in Iraq’s political class.

Iraq’s new prime minister, Mustafa al-Kadhimi, was a friend of al-Hashimi in life, and was affected by his death. Al-Kadhimi promised an investigation to find al-Hashimi’s killers. The investigation is yet to bear fruit.

Dissent in Iraq is a dangerous business. It often brings violence in its wake. But al-Hashimi did not fit the profile of many Iraqis targeted by an extraordinary series of political murders, in what has become a year of assassination. This spate of violence is more than mob violence, or the result of troubled times which still contain a threat from the surviving Islamic State. Instead, it dates to the beginning of large-scale protests in October last year.

It was largely Iraq’s youth which, from late last year, filled squares and chanted slogans. They had grown up in two decades of war and poverty, exacerbated by a series of incompetent governments, and presided over by an elite increasingly openly in hock to Iran.

These protests were violently put down by mystery gunmen, notably in Tahrir Square in Baghdad, where hundreds of protesters were shot with live ammunition last year. Some were deliberately hit with tear gas cannisters, shattering their skulls. A number of activists and journalists who left the protests were followed by men on motorbikes and shot as they returned to their homes.

Al-Hashimi supported the protests and criticised the influence of Iranian-sponsored militias on Iraqi politics, but his moderate tone, and closeness to the heart of Iraq’s public life, made the shock of his murder all the greater.

In Basra, in Iraq’s south-east, where protests against adverse local conditions have simmered for months, the murders are more routine. Last week, Tahseen Ali, an activist, was fatally shot. Three days later, a friend of his, Ludia Remon, was also attacked but survived.

That Iran is willing to assassinate domestic protesters in Iraq suggests both a power of action and also fear

This week, Reham Yaqoub, a young medical worker from Basra and a prominent figure in the city’s protests, was shot by an unknown assailant. The same day, four other activists were murdered: three in Basra, and one in Baghdad. Not long ago, Iran’s Mehr News Agency had alleged that several protesters in Basra were agents of the American consulate in the city. It ran Yaqoub’s photograph in accompaniment. It was soon widely reported that, in the past year, all five of those killed had met American representatives.

In Basra and across the country, the identities of the would-be assassins are officially unknown. But they are hardly difficult to discern.

Ali, Remon, Yaqoub and other demonstrators were consistently threatened with death by militia leaders, and have been roughed up by militia muscle, since protests began. When demonstrations began in October, those participating were targeted by snipers. Military officials denied responsibility and all knowledge of what was going on. They seemed rather uncomfortable at having to do so in public.

The snipers were later linked in no uncertain terms to Hashd al-Shaabi, a militia umbrella group formed in the campaign against the Islamic State and closely tied to Iran, by two Iraqi officials anonymously speaking to Reuters.

Before he was killed earlier this year, alongside the general and mastermind of Iran’s network of proxies across the Middle East Qassem Soleimani, the leader of Hashd was Abu Mahdi al-Muhandis. Muhandis led the Hezbollah Bridges, an Iranian proxy as overtly proud of its sponsors as it is threatening to Iran’s enemies. There is little doubt about where its loyalties lie.

There are limits to what even willing politicians can do when no one is invulnerable

That Iran is willing to assassinate domestic protesters in Iraq suggests both a power of action and also fear. Iran’s capture of the Iraqi state is remarkable and was exposed in a series of leaked documents earlier this year. Militiamen run government departments and oversee the bureaucracy. Their armed mobs refused to disband or to disarm after the declaration of victory against ISIS almost three years ago. Theirs is a remarkable story of state capture, only recently undercut by international notice and domestic opposition.

Iran is both comfortably powerful enough to kill on Iraq’s streets without its influence being acknowledged and its agents prosecuted, but still feels sufficiently threatened by civic action that a campaign of murder is deemed necessary to protect its stake.

Militia violence against protests is remarkably brutal, and makes shocking reading, but could be considered almost an instinctive gesture of an occupying power; even the natural reaction of a foreign-sponsored force determined to preserve its position in Iraq by putting down popular opposition.

Killing demonstrators at the site of their protests is intended to make protesting a dangerous activity and to keep people away from the barricades. Al-Hashimi’s murder was more flagrant and more extraordinary. He was a fixture of Iraqi national life with real proximity to power.

Though al-Hashimi was a critic of the militias’ overreach, he could likely have been mollified. But Iraq’s year of assassination leaves no room for assimilation. The widespread killings of journalists and activists, and of a scholar who was close to protests in thought and speech only, introduces a different kind of crime.

It speaks of a militia movement acting beyond the law and outside the bounds of a state its people have already taken over. The militias are not, as some had hoped, weakening and retreating in light of popular criticism and the death of Soleimani; instead they are retrenching, and demonstrating new willingness to kill with impunity.

Al-Kadhimi’s government has declared hundreds of those killed in demonstrations last year “martyrs” and has moved to provide financial support for their families. There is even talk of prosecuting the odd militia member who took pot shots at the protests.

But as al-Hashimi’s unsolved assassination has shown, there are limits to what even willing politicians can do when no one is invulnerable, even a friend of those in office. And while all this is discussed by those in office, the power remains with those armed groups which operate beyond the law, and at the behest of a foreign power.