The why is really rather simple. Bomb a military barracks and you may kill a few men. Bomb a hospital and you will kill many times more as those wounded in future attacks have no place to be treated. Bombing hospitals is a great casualty multiplier. Attacking hospitals is second only to torture as the most commonly committed war crime.
World War I
The earliest instance of the aerial bombing of a hospital was on May 31, 1918 when the Germans bombed the rear echelon hospital complex at Etables in the Pas-de-Calais, France.
World War II
sunk the hospital ship St. David (pictured) on January 24, 1944.
Korean and Vietnam Wars
The US Air Force engaged in extensive strategic bombing of urban targets in both wars. Operation Rolling Thunder during the Vietnam War was famously intended to bomb North Vietnam "back to the Stone Age." During that war, America bombed the Bach Mai Hospital in Hanoi. It was later rebuilt with money largely donated from the United States.
Yugoslav Civil War
NATO got bomber happy in their efforts to protect civilians from ethnic cleansing. NATO bombed over 20 hospitals, as well as over 200 schools, in less than three months of extensive bombing. Some hospitals appear to have been accidentally hit but, given NATO's pride at the "precision bombing" and their targeting of "dual use" facilities, most of the hospitals were deliberately bombed.
During the second Gulf War, American forces bombed a maternity hospital in Baghdad in April, 2003. Many other hospitals and clinics had been bombed in the years between the Gulf Wars. In May, 2012, the Iraq government dropped barrel bombs on an hospital in Fallujah as part of the ongoing civil war in Iraq.This month, the Iraq government has bombed hospitals in several towns including Tikrit and Shirqat.
2009, they bombed three hospitals including fire bombing the Al Quds Hospital (pictured) with white phosphorus. The use the same excuse that NATO gave in Yugoslavia, dual use facilities. Most recently, Israel bombed the Shifa Hospital in Gaza.
Syria Civil War
|The Kindi Hospital in Aleppo was destroyed by two suicide bombers in December, 2013.|
It doesn't take an air force to bomb a hospital. Many have been bombed by terrorists and insurgents. The Taliban has bombed hospitals in Afghanistan. Somali rebels bombed a hospital in Mogadishu. In 1991, the IRA planted a bomb in the military wing of the Musgrave Park Hospital in Belfast, killing two and wounding 11 including a four month-old baby.