A couple of mottos i remember

[EuroSpike]

Perhaps the most popular ones.

Jos vihollinen ei tule idästä, se on koukannut. (If enemy doesn't come from the east, its flanking).

Ryssä on ryssä, vaikka voissa paistaisi. (Ruskie is a ruskie even if fried in butter).

Hiki säästää verta. (Sweat saves blood).

 

[AFSteliga]

Interesting ones, but good nonetheless.

 

[EuroSpike]

Interesting ones, but good nonetheless.

Actually they are more folk sayings than military mottos but work as mottos aswell. Very popularly used anyway.