During the battle of Midway, the US sent 3 torpedo squadrons to attack the Japanese fleet. Almost all were lost. Was this a planned suicide...

I would argue that this was not a planned suicide attack. 
Instead, it was an attack that the US launched using some of the very few weapons that
the US possessed.

In 1942, the US had not yet managed to
seriously upgrade its weaponry or to train a large group of highly qualified pilots. 
The US was not nearly as ready for a war as Japan had been.  Because of this, the US was
forced into fighting in relatively disadvantageous circumstances.  The Devastators that
these pilots flew were no match for the Japanese aircraft and there were not enough
fighters to provide cover.  Many of the fighters available to the US at Midway were
Brewster Buffalos which were terrible overmatched by the Japanese planes as
well.

So, the attack was not a planned suicide attack.  It
was a desperate attempt to hold the Japanese off using what weaponry was available to
the US at the time.