The explosion at the al-Ahli Arab Hospital in Gaza City on Tuesday was the latest in a growing series of violent incidents involving medical facilities in conflict zones, which together have taken an enormous toll on vital health care infrastructure and staff in violation of what was once a bedrock aspect of international law.

Over the past two decades, as the principle of sparing health care workers and facilities has continually eroded, the most dangerous incidents have been carried out by state actors, said Michiel Hofman, an operational coordinator for Doctors Without Borders in Sudan and a veteran of medical aid delivery in Afghanistan, Yemen and Syria.

Yet Article 18 of the First Geneva Convention, ratified by United Nations member states after World War II, says that civilian hospitals "may in no circumstances be the object of attack, but shall at all times be respected and protected by the parties to the conflict.”