How did U-boats impact WW1? It was the first undetectable ship, and only had to surface when attacking during combat. Without it's invention, the war would have ended very differently, with Brittan being able to transport virtual all their supplies to the front lines, unhindered.This could have allowed Britain to win far faster than they did.
undetectable, could stay out for 2 months at a time, cheap to produce Cons:
had to surface to fire torpedos, limited space, had to reload torpedoes by hand
I must confess that my imagination refuses to see any sort of submarine doing anything but suffocating its crew and floundering at sea. — H. G. Wells