…if it is the same weapon…
When it comes to spears, it usually wasn't. People tend to think all spears are the same but they do vary. A lot. You wouldn't want to go into melee with a throwing spear, as they tend to break at impact (and were designed that way, to avoid being thrown back), whereas, whilst you may carry a long spear with one hand for travel, it'd be just too heavy or, well, long to be used on foot with one hand. Others are specifically designed to be used from horseback, or one-handed but together with a shield and only in formations, not individual combat.
In a nutshell, one probably wouldn't use the same spear to throw at enemies, fight from horseback, fight in individual combat, or fight in formations.
As Musashi said,…
Musashi
created the Nitō Ichi sword style, when
every single other swordsman was using a katana two-handed, so I wouldn't really quote him in this matter.
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