(Melina Mara/The Washington Post)

Hillary Clinton delivered what her campaign billed as a "major" foreign policy speech Thursday in California. But what the speech seemed primarily concerned with was taunting presumptive Republican nominee Donald Trump as a know-nothing blowhard who is way out of his depth when it comes to international matters. It was startlingly effective.

From the start, Clinton abandoned her typically cautious language. She called Trump "dangerously incoherent." She said he "doesn't have a clue." She described his foreign policy as "a series of bizarre rants, personal feuds and outright lies." She did this: "I will leave it to the psychiatrists to explain his affection for tyrants."

Over and over (and over) again, Clinton cast Trump as a brash-talking buffoon who has "no clue" about foreign policy or how the world works more broadly. And it continued after the speech, too!

What Clinton seemed to be signaling in the speech was less that she and Trump have very different visions of America's role in the world, which they do, and much more that she could fight fire with fire. That if Trump wants to call her "Crooked Hillary," she will call him "no clue" Donald. That if he wants to turn this campaign into a war of (nasty) words, she's ready to go taunt for taunt.

That's a smart strategy for two reasons.

First, savaging Trump in unusually (at least for Clinton) blunt terms helps rally Democrats behind her. With the California primary looming and Bernie Sanders still lingering on Clinton's left flank, the best thing she can do is try to focus the lens on the common enemy: Trump. It's hard for me to imagine any Democrat watching Clinton's speech on Thursday and not feeling more favorably inclined to her by the end of it. The enemy of my enemy is my friend is a powerful piece of logic in primary politics and one that Clinton very effectively deployed in her speech.

Second, Clinton seemed to go out of her way to needle Trump as aggressively as she could without venturing into Marco-Rubio-small-hands territory. It was all part of a strategic effort to get under the real estate mogul's skin, which, as the Republican primary revealed, isn't all that hard to do. (Clinton even hinted in the speech at what she was doing — noting that Trump has "thin skin.") An angry Trump, the Clinton team believes, is a Trump who makes mistakes and a Trump who is less than appealing to a general electorate.

What the speech also did is serve as a reminder that Clinton is best as a candidate when she is on the attack. Part of the reason she has struggled to put away Sanders is that she can't, really, go after the senator for fear of alienating his liberal supporters ahead of the general-election fight to come. When Clinton is able to go full bore at someone — as she did with Trump on Thursday — she clearly relishes it.

If this was a peek at the general-election version of Clinton, Democrats have every reason to be excited. This was one of her strongest performances of the campaign.