If germany had been more successful in the battle of the atlantic, what would have happened?

If the battle of atlantic had been a victory for Germans, all British trading routes would've been blocked, which would mean that they would lose all access to things like food eventually and that they would be starved out.

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen