Highest number of military casualties in a single event (peacetime)?

What are examples of military incidents, accidents, maneuvers, exercises etc. that cost the lives of an unusually high number of soldiers (airmen, sailors, marines) or civilians during peacetime? “Peacetime” in this context may also refer to an incident during times of war, but removed from an actual theater of war (i. e. were the fighting takes place).

Since I assume that losses of ships and aircrafts will rank high on that list, let’s differentiate:

a) naval
b) aviation
c) land

Technically, they were on their way to start a war, but the term “kamikaze” (divine wind) originally refers to two attempts by the Mongols to conquer Japan. In both cases, the Mongol ships were sunken by massive typhoons, and Japan was spared.

The second fleet (according to the Wikipedia) had 140,000 men.

https://en.wikipedia.org/wiki/Kamikaze_(typhoon)

After the Civil War the steamboat Sultana was estimated to have around 2,100 recently released Union prisoners of war on board when its boilers exploded on April 27 1865, killing around 1,800.

A munitions ship exploded in Halifax, Nova Scotia in 1917, killing about 2000.

Er, I misread the question, please disregard.

I’m not sure whether the Salang tunnel explosion meets your criteria (of being outside a theatre of war). It was in any event an accident and not an act of war, and resulted in the deaths of thousands of Soviet soldiers.

I think it’s obvious that I also misread the question, only not in time to edit. :o

I think the likely answer is going to be some incident of disease breaking out in an army. Diseases used to kill more soldiers than combat did.

Probably true, but the OP asks for “military incidents, accidents, maneuvers, exercises” and I don’t think disease fits those categories.

What I had mind were incidents like this one: 80 soldiers (mostly young recruits) and one civilian drowned on March 31st, 1925 during a Reichswehr exercise when a ferry boat capsized on the river Weser near Veltheim, Westphalia (in northwestern Germany).

There is a small monument and a plaque in honor of the victims:

http://static.panoramio.com/photos/original/20209612.jpg

From what I have been able to gather, this was the biggest loss of life during peacetime in German military history.

Arrow Air Flight 1285 was a chartered DC-8 returning the 3rd/502 Infantry battalion of the 101st Airborne to Ft Campbell in December 1985 from UN Sinai duty. It crashed on takeoff from Gander in Canada. 248 soldiers and 8 crew dead.

I was in the 2nd/502 at the time and had the unpleasant task of carrying the casket of the first soldier buried. It was an icy cemetery in West Virginia and his mother did not stop screaming.

There was a collision in 1887 between two British battleships HMS Victoria and HMS Camperdown where 358 sailors drowned.

http://ahoy.tk-jk.net/macslog/StupidityreignsandthenAdm.html

Well, Halifax was pretty far from a theater of war, so your example met the OP’s definition.

Likewise the Port Chicago disaster in 1944.

Yes , of course. Thanks for reminding me (us) of that terrible day.

ETA: Thank you for your service.

I was going to post the same incident, till I saw your post.
My brother was on that plane.
My deepest regards to you for doing one of the more emotionally draining duties in the military.

While it didn’t have nearly the number of casualties of some of these incidents the Green Ramp Disaster was pretty horrific. At Pope Air Force Base a crashing F-16 covered waiting 82nd Airborne paratroopers in burning jet fuel and debris. 24 died and 80 injured. Many of the survivors were horribly burned.

I’m not sure if this fits the OP’s criteria either, it was in war-time but during an exercise:

https://en.wikipedia.org/wiki/Exercise_Tiger

Royal Navy has had its moments

https://en.wikipedia.org/wiki/Scilly_naval_disaster_of_1707

The [https://en.wikipedia.org/wiki/Quintinshill_rail_disaster](Quintinshill rail disaster) killed more than 200 soldiers in the Scottish borders. The total number was never 100% confirmed because a) big fire, b) the regimental paperwork was on the troop train that burned.