Fuse needed to prevent too much current draw in DC motors?
A good bridge is &lt; 0.1 Ohm and good batteries @ 50 mOhms while the motor DCR will be 10% of rated V/I  = 10% * 8/0.25= 3.2 Ohms thus Isc= 6V/(0.1 + 0.05 + 3.2 )= 1.8A per motor pole surge current.

But if the motor port is shorted, Isc= 6V/(0.1+0.5) = 40A

So a 10A fuse makes sense.