I'd suggest there is no such thing as unprovoked. The attacker always responds to something he found offensive. In Japan's case, it was the oil embargo and an exaggerated sense of entitlement. Justification is the variable.
It would be a foolish aggressor who telegraphed his intentions to attack, surprise being one of the most important aspects of engagement.
An unprovoked attack by North Korea on South Korea in June 1950
Type your answer here... Germany did an unprovoked attack on Poland
Us declare war on the Japenese? They attacked us! We merely defended ourselves against an unprovoked attack with a bang.
Pre-emptive strike
Congress declared war on Japan because of that country's unprovoked attack on Pearl Harbor on December 7, 1941.
Type your answer here... Germany did an unprovoked attack on Poland
The unprovoked attack by the Japanese on Pearl Harbour
An unprovoked attack by North Korea on South Korea in June 1950
The unprovoked attack on Pearl Harbour by the Japanese
North Korea with it's unprovoked attack on South Korea on June 25, 1950.
The first attack, or act of hostility; the first act of injury, or first act leading to a war or a controversy; unprovoked attack; assault; as, a war of aggression. "Aggressions of power."
The attack was treacherous for many reasons. The United States was engaged with Japan in negotiations over the war effort. The attack was unprovoked and was unexpected.
The prime minister of Britain declared war in Germany. The world war 2 started by Germany in a unprovoked attack on poland.
Us declare war on the Japenese? They attacked us! We merely defended ourselves against an unprovoked attack with a bang.
Pre-emptive strike
Congress declared war on Japan because of that country's unprovoked attack on Pearl Harbor on December 7, 1941.
If you are talking about our current war, then yes, it would. The U.S. launched an unprovoked* attack on another country. This is definitely seen as an act of war, even if done with good intentions. *The provocation was a relatively small terrorist group, not the country as a whole, therefore, it could be seen as unprovoked.