A passage on the relationship between Zen and Budo, from the writings of Omori Sogen Roshi:
A person once asked [Yamaoka] Tesshu [the famous 19th century Zen, sword and callligraphy master], “What is the secret of swordsmanship?” Tesshu answered, “It is entrusted to the Asakusa Kannon.”
He at once went to Asakusa and searched everywhere in the temple and came to realize that the sign [i.e. calligraphy above the altar] with the words Se Mu I [Se—give; Mu — negation, absence; I — fear, that is, "giving fearlessness") must be it. When he repeated this to Tesshu it is said that Tesshu answered “kekko” (very well) and laughed.
Fearlessness is the removal of fear and anxiety from the kokoro [mind, heart] of people. To say it another way, it is to give absolute peace of mind.
If the highest stage of swordsmanship is to give Fearlessness, then it is completely the same as Zen. The question is in the process to attain that state.