In title and content alike, Let England Shake trembles with fair measures of arrogance, doomsaying, and felicity: it dares to assign itself a not inconsiderable degree of impact, to declare a state of emergency, to be lithe and elastic enough to enliven a senior center mixer. Given Polly Jean Harvey’s propensity for viscerally cruel or cutting narratives of an inward-looking nature, her decision to cut an explicitly political album is shocking. More startling is how festively fetching the Great Britain-demonizing anthems she and her autoharp furiously strum into being are, how easily they trick one into toe-tapping. See the title track’s chime-drenched flounce and merrily-down-the-drain smirk, the amiable bass-section shuffle, and drolly related battlefield horrors that dot “The Words That Maketh Murder,” and the dregs-of-war reggae drone that informs “Written on the Forehead,” where Harvey’s voice seems to ooze up through several layers of rubble. Her homeland’s her prime target, for sure, but in a larger sense, Harvey’s looking down her nose at the very concept of empire. Redolent of Stereolab’s thrumming “Mountain,” the spritely, jangling “The Glorious Land” dryly envisions the United States and England — fading empires, both — as codependent bedfellows. “What is the glorious fruit of our lands?” she asks, before answering her own question over a beat you could tango to: “Its fruit is orphaned children.” Harvey’s coming-out party is an alluringly acidic wonder, nothing short of a late-career revelation.