Taiji Sword (太極劍) by Wu Tunan (吳圖南) - Translation: Scott M. Rodell

From the introduction to Taiji Sword (太極劍) by Wu Tunan (吳圖南) -

夫劍法無運用不能因敵致勝，微變化焉能出入神奇。是以初學劍術者，或姿勢不正確，或動作不自然，或應用不純熟，或轉換不玲琍。是皆由於不知運用之變化使然也。蓋用劍之法，紐勁為上，靈捷為先。目宜速，身不可滯。手宜敏，步不可遲。 久之，自然動作儒雅，舉止大方。其形勢似飛鳳。其勁力透中鋒。使用腰力，運動全身。故發勁用勢，非僅徒用手指着力而已耳。

Those practicing sword who do not practice applications can not achieve victory over different types of enemies,*(*There are different types of swordsmen and one must practice applications to deal with them in different ways analysis each, then taking advantage of their weakness.) (without practicing applications) if the enemy makes little changes you can not move the sword in and out with miraculous skill.
Therefore, when first studying the sword art, maybe the postures are not correct, maybe the movements are not natural, maybe the applications not skillful, maybe the changes are not nimble. This is all due to not knowing the changes in applications. Concerning the application of sword techniques, the higher skill is turning power, being spirited and quick is also a priority. The eyes must be fast, the body cannot be sluggish. The hands must be agile, the steps cannot be late. After a long time, your movements naturally become refined, with a graceful bearing. Your postures resemble a flying phoenix. Your power passes through your center. Use the power of the waist, move the entire body. Therefore, when releasing power in a movement, do not merely use the power of the hand.

Translation: Scott M. Rodell