Came close to not being enough, even then.

https://en.wikipedia.org/wiki/Ky%C5%ABj%C5%8D_incident

The Kyūjō incident (宮城事件, Kyūjō Jiken) was an attempted military coup d'état in the Empire of Japan at the end of the Second World War. It happened on the night of 14–15 August 1945, just before the announcement of Japan's surrender to the Allies. The coup was attempted by the Staff Office of the Ministry of War of Japan and many from the Imperial Guard to stop the move to surrender.

The officers murdered Lieutenant General Takeshi Mori of the First Imperial Guards Division and attempted to counterfeit an order to the effect of permitting their occupation of the Tokyo Imperial Palace (Kyūjō). They attempted to place Emperor Hirohito under house arrest, using the 2nd Brigade Imperial Guard Infantry. They failed to persuade the Eastern District Army and the high command of the Imperial Japanese Army to move forward with the action. Due to their failure to convince the remaining army to oust the Imperial House of Japan, they performed ritual suicide. As a result, the communiqué of the intent for a Japanese surrender continued as planned.

They tried to seize the recording of Emperor Hirohito's surrender speech before it could go out:

The rebels, led by Hatanaka, spent the next several hours fruitlessly searching for Imperial Household Minister Sōtarō Ishiwata [ja], Lord of the Privy Seal Kōichi Kido, and the recordings of the surrender speech. The two men were hiding in the "bank vault", a large chamber underneath the Imperial Palace.[15][16] The search was made more difficult by a blackout in response to Allied bombings, and by the archaic organization and layout of the Imperial House Ministry. Many of the names of the rooms were unrecognizable to the rebels. The rebels did find the chamberlain Yoshihiro Tokugawa. Although Hatanaka threatened to disembowel him with a samurai sword, Tokugawa lied and told them he did not know where the recordings or men were.[12][17] During their search, the rebels cut nearly all of the telephone wires, severing communications between their prisoners on the palace grounds and the outside world.

The morning the bomb was dropped on Nagasaki, another thing happened: Russia declared war on Japan, invaded, and had made huge progress in the night. There's some evidence the guys at the meeting who decided on surrender had not heard of the Nagasaki bomb yet, though the bombs are the official reason Japan gives for surrender.