Up to that time, attacking Guernica was "unparalleled in military history." Heavy bombing panicked people. Machine gun strafing drove them underground. Incendiary bombs destroyed their hiding places. Everything going on was horrifying.
"When I entered Guernica after midnight, houses were crashing on either side, and it was utterly impossible even for firemen to enter the center of the town."
"The hospitals of Josefinas and Convento de Santa Clara were glowing heaps of embers. All the churches except that of Santa Maria were destroyed, and the few houses which still stood were doomed."
"When I revisited Guernica this afternoon most of the town was still burning, and new fires had broken out. About 30 dead were laid out in a ruined hospital."
Guernica was history's first city destroyed by terror bombing. Civilian men, women, and children were deliberately targeted. Military expert Wolfgang Schmidt told Der Spiegel :
"For the German air force, Guernica was a trial run on how one can spread horror and distress through attacks on cities and towns."
"Of course," bombing the city "was a blatant violation of human rights and had a terrorist character. It was accepted that civilians would be harmed."
It was worse than that. They were deliberately targeted to inflict mass casualties.
A third or more of the population of 5,000 was either killed or wounded. Almost three-fourths of Guernica's buildings were destroyed or heavily damaged. Fires engulfed the city. They burned for three days. Area farms were bombed.
A survivor said:
"The air was alive with the cries of the wounded. I saw a man crawling down the street, dragging his broken legs."
"Pieces of people and animals were lying everywhere."
"In the wreckage there was a young woman. I could not take my eyes off her. Bones stuck through her dress. Her head twisted right around her neck. She lay, mouth open, her tongue hanging out. I vomited and lost consciousness."
Guernica had no strategic significance. Hitler's bombed it for target practice. It was dress rehearsal for WW II. Wehrmacht generals flexed their muscles. They signaled what lay ahead.