Think of the most indestructible thing in the known universe. Right? Well, a squaddy can break it. Think of the same thing, but put it through a 20 year 2 billion pound development. Got that thought in your head? Well, the same squaddy can still break it. Squaddy proofedness is thus the holy grail of defence contractors, and any claim to have achieved this state of nirvana is construed as a challenge. No-one has ever succeeded in this challenge.
In the great annals of British military history, the one device to have almost achieved the Seventh State of Squaddy Survivability was the SLR rifle, but even this near perfection could still be broken by a strong-willed tom. (FB says "I saw it happen. An old Bdr had to get his squad across a barbed wire obstacle. Having seen loads of WW2 films where this was done, using rifles as a sort of step ladder, he tried the same. Obviously the SMLE was nearer level 7 SSS than the SLR, as our SLRs never worked again afterwards)
The rubber eye piece for one of the old Starlight scopes was thought to be squaddie proof, it's rubber nothing to go wrong...so bored squaddies would eat it. So close but no cigar.
According to un-named Government sources, the only item ever to have been given to a squaddy and returned undamaged (i.e. the only squaddy-proof item EVER) was the ball bearing!
Any rumours that BFG 9000 may once have melted a 3/4" ball bearing with some jump leads & a 255kVA Generator are grossly over exaggerated. It simply sparked and shed a few grammes, did it?
If, and only if, a piece of equipment reaches the 7th SSS, then, with true inevitability, it will get lost.
When something that is to be Squaddy Proof, designers should remember that even Squaddies undergo evolution. The old adage "Make something idiot proof and someone will make a better idiot" should be kept in mind here.