查一下美國的國際法，是這樣的

Under U.S. law and international norms, the U.S. is not strictly required to declare war before conducting military strikes—especially if the operation is framed as:

• Self-defense (under Article 51 of the UN Charter),

• A limited military action, or

• A response to attacks on U.S. personnel or allies.

1. U.S. Constitutional Law

• Congress has the sole power to declare war (Article I, Section 8).

• But presidents often authorize military action without a formal declaration of war, citing:

  • The War Powers Resolution of 1973, which allows the President to use force for up to 60 days (plus 30-day withdrawal) without Congressional approval.

  • Existing Authorizations for Use of Military Force (AUMFs), such as the 2001 or 2002 AUMFs, which are sometimes stretched to justify strikes.

2. Recent Practice

The U.S. has not declared war since World War II. All subsequent conflicts—including:

• Vietnam,

• Kosovo,

• Iraq (2003), and

• Syria/Iraq/Iran-related operations—
  were carried out under AUMFs or executive authority, not a formal war declaration.

3. International Law

Under the UN Charter, force is only legal if:

• It is in self-defense, or

• Approved by the UN Security Council.