Updated April 07, 2017 21:04:36

Proportionality. US Presidents are expected to measure how they unleash their deadly military might with some degree of size and devastation which relates to the event they are seeking to avenge.

In the modern era US attacks on a foreign government's military or its installations are rare outside of declared wars.

Look back at the events as they unfolded in our blog.

Donald Trump, Syria 2017

• NO warning
• TWO DAYS response before bombing

US President Donald Trump has limited his surprise cruise missile attack to a military target.

It comes two days after a chemical weapons attack that the US blames on the Syrian government.

The Americans say it was that airfield from which the Syrian air force launched the chemical weapons attack.

Barack Obama, Syria 2012-2013

• ONE YEAR warning
• NO bombing

The missile attack came after years of heated debate and deliberation in Washington over intervention in Syria's bloody civil war.

In 2012, President Barack Obama declared a "red line" that if Syrian President Bashar Al-Assad used chemical weapons on his people it would justify an American military response.

In 2013, after a chemical weapons attack by the Assad regime killed almost 1,500 civilians, Mr Obama chose not to launch strikes.

Instead, he went to Congress to seek an authorisation.

That authorisation never came, but it did result in Russia offering to broker the removal of Syria's 1,300 tons of chemical precursors and agents.

Ronald Reagan, Libya 1986

• Weeks of warning
• NINE DAYS from incident before bombing

President Ronald Reagan warned Colonel Gaddafi he "would hold his regime accountable for any new terrorist attacks launched against American citizens".

Weeks later, on April 5, a terrorist bomb killed American servicemen.

Photo: In 1986 Ronald Reagan told Americans he had launched "a series of strikes" against Colonel Qadhafi. (Reuters: Stelios Varias)

Nine days later in an address to the nation, President Ronald Reagan told Americans that he had "launched a series of strikes against the headquarters, terrorist facilities, and military assets that support Muammar Gaddafi's subversive activities".

He said "the attacks were concentrated and carefully targeted to minimize casualties among the Libyan people with whom we have no quarrel".

Immediate reports that Gaddafi's daughter was killed in the strikes were later downplayed about whether she actually existed.

Two US airmen were killed when their F-111 was shot down by the Libyans.

The takeaway:

Compared to other presidents Mr Trump has gone for a quick military action against the Syrian air force — highly likely killing Syrian military personnel, possibly Russian personnel — without seeking the counsel of Congress.

His advisers will have calculated that this will be popular domestically — differentiating him from Obama.

It will raise the risk that American military personnel or their planes or those of their allies — Australia included, who are operating missions in Syrian airspace against ISIS — may be targeted in response.

Topics: donald-trump, unrest-conflict-and-war, world-politics, united-states, syrian-arab-republic

First posted April 07, 2017 15:21:29