You can’t retreat from an amphibious assault, so I don’t understand what you mean by your statement.
land in normandie because germany has no counterattack
pull out of normandie the next round when they have built up a counter attack.
one of the most “conservative” things I do is to not make 60% attacks for the game if I feel I have more than 60% chanse of winning without doing it.
similarly, giving my opponent the ability to do a 40% attack for the game, if i feel I have more than 60% chance of winning the game without letting him do it. Anoter problem with the 40% attack is that if he can withdraw, it can be a good idea for him to do it. (because then he can do the first combatround and see how it goes).
the main thing I think of as conservative is to not build flashy units, but focus on the cheapest way to get the volume needed at the place needed. like not building many tanks with germany, building more ftrs than tacs for the sea (because it is all about being able to withstand the opponents navy IMO), not building BBs and CAs in general. only building the number of CVs needed, not more (bc there are usually better units for fighting at sea /ipc).
and in general trying to deny the opponent the ability to do good attacks, rather than doing marginal attacks myself.