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).

Interesting ones, but good nonetheless.

Originally Posted by NCdt Steliga

Interesting ones, but good nonetheless.

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