Alpine War

The Alpine War was a military conflict between Switzerland and the Axis Powers, lasting from April to May of 1947. Switzerland fought solely in their alpine forts for the entirety of the war, inflicting heavy casualties on their attackers, but were ultimately unable to hold out without help from the air. The Wehrmacht and Royal Italian Army's inability to quickly force a surrender on the Swiss led to major reforms in both countries high command.

Declaration of war and Swiss retreat
Upon learning of the Axis declaration of war, Henri Guisan ordered the Swiss army to leave the border regions and retreat to their forts in the Alpine, knowing that facing the Axis in level ground would be suicide. The same day, Liechtenstein surrendered without a single bullet being fired.

Once the Swiss border regions were captured, Germany and Italy ordered only their mountain troops, who made up less then a quarter of the attacking forces, to continue to the Swiss forts. This decision was largely due to the Axis not knowing of the Swiss retreats, and had assumed the Swiss army was so tiny they were unable to man their borders.

Battle of the Alps
The most brutal fighting of the conflict, the Alps began claiming lives the minute of Axis arrival on April 21st. Not expecting the Swiss to be as dug in as they were, mass confusion was reported in the German and Italian High Command as they attempted to coordinate any type of assault until calling a retreat days later. It's estimated that between 10,000-30,000 Axis soldiers were killed in the initial assault.

These assaults continued for another 22 days. Commanders would assemble thousands of soldiers and throw them at the Swiss forts, hoping for any type of territorial gains. At the end of an assault, which would often last several days, little would show for the thousands of soldiers dying in battle, while the Swiss were left with little losses. Small skirmishes also took place in Zurich and Bern until May 3rd and 11th respectively, which led to the former being firebombed by the Luftwaffe.

German air superiority and victory
Once air superiority was gained, German bombers were able to destroy the Swiss forts. Commanders would follow up the bombings with an attack from their infantry. Usually though, these attacks would be little more than a quick sweep of the forts as the Swiss occupying it would have already retreated or been killed in the bombing.

This cycle repeated for another 17 days, until on May 30th the Swiss finally surrendered to the Axis, being split between Italy and Germany.

Aerial Warfare
Aerial warfare was arguably the winning factor for the Axis, allowing the Luftwaffe's bombers to destroy the Swiss forts. However, even without an air force the Swiss put up a valiant fight in the air.

Numerous AA guns were spread around the Swiss forts, usually heavily fortified, and fighters were forced to take the majority of these out before bombings could be carried out successfully. Even this simple sounding task took weeks, as fighters had trouble identifying the locations of the AA guns before they were shot down. Once the majority of the AA guns had been destroyed, bombers had a clear opening to destroy the Swiss forts.

With the destruction of these forts, the Swiss lost their only advantage, and surrendered 17 days later on May 30th.

Hungary
A portion of the Hungarian 2nd Army, mostly consisting of veterans from the Battle of Stalingrad, was sent to Germany and placed under its command. Although never meant to fight in the Alps, when the situation worsened the second army was forced to help in taking the Swiss forts. Again, even without proper mountainous training and equipment, the Hungarians proved their worth when, in a single day, they took 3 Swiss forts without bomber support. This was one of the only cases of the Swiss losing ground before the Germans gained air superiority.

Romania
100 fighters from the Royal Romanian Air Force were sent to assist the Luftwaffe. 22 had been shot down by the wars end.

Vichy France
French medical personnel treated wounded soldiers in field hospitals away from battle.

Atrocities
While the Swiss army held out in the Alps, German and Italian soldiers would often rape and kill Swiss civilians in occupied cities. This was likely done in response to the trauma inflicted upon soldiers as they lost friends and received life changing injuries, which they blamed on the Swiss people.

Bern was firebombed by the Luftwaffe on May 10th. Bern had been the last remaining Swiss held city outside of their Alpine forts, and German High Command considered the capture of the city crucial. However, like in the Alpines, the Swiss fought for every inch of the city with unmatched bravery. After a 20 day siege, German commanders ordered the city to be firebombed. The Germans claimed victory the next day, containing the fire inside the city but letting Bern itself burn to the ground. The fire was put out after the Swiss surrender on May 30th. During the fire, civilians were sealed inside the city by the Germans, with very few escaping. By the time of the fire being put out most of the cities population had died.

Germany
Most German soldiers lost their life during the brutal fighting in the Alps, where the average lifespan of a soldier was just 8 hours. Large casualties were also taken in Bern, where Swiss defenders held out against a German encirclement for 20 days. By wars end, 30,000 German soldiers had lost their lives while 15,000 were wounded, the most of all combatants. As well, 521 airmen of the Luftwaffe were shot down by Swiss AA guns.

Italy
Like Germany, most Italian deaths came from the Alps. The average Italian soldier, however, had a higher life expectancy at 15 hours. Italy had lost 15,000 soldiers and had 17.000 wounded.

Switzerland
Although at first suffering little casualties, once the Germans gained air superiority Swiss casualties skyrocketed. 40,000 were killed and 20,000 were wounded by the time they surrendered, with the remaining 60,000 were likely taken to POW camps.

United States
United States President Harry Truman publicly demanded that Germany and Italy cease their attacks on Switzerland or face Allied intervention. Although no response to this statement was given by Germany or Italy, an Allied intervention never occurred. Truman later accused the Axis of having no intention of repairing relations with the west, a theory that has been furthered with the Axis Powers interference in Brazil.

Japan
After the Swiss surrender Japan began slowly distancing itself from the Axis, starting with limiting its trade to Europe. Although the Iranian Crisis is seen as the final nail in the coffin for Japanese relations with the Axis, the Alpine War is generally seen as what took them to the boiling point.