Personally, the former sentence emphasizes the importance of strict training tactics in peacetime, while the latter sentence emphasizes the determination of fighting will and the samurai spirit of cross the rubicon. Figuratively speaking, the previous sentence can be understood as "We usually train hard, sharpen our will and strengthen our tactics and strategies, so we can defeat the enemy on the battlefield, no matter whether the number of the enemy is several times ours." I think the understanding of the latter sentence should be: "No matter how powerful and unshakable the enemy looks, we will go all out to fight, even if we sacrifice our own flesh and blood, and we will never show weakness."

Personally, I prefer pure samurai spirit, which has nothing to do with militarism. LZ is advised to watch The Last Samurai, in which Tom Hanks wrote in his diary: "They (Samurai) try their best to do what they should do every morning." I think it echoes the first sentence. At the end of the play, the warrior's tragic and desperate charge perfectly explained the last sentence you said.

It's all personal understanding, for communication reference only.