These were originally included in the book Journey to a War, which was according to biographers mostly authored by Auden's traveling companion, the writer Christopher Isherwood. The book was published in 1939; their travels were commissioned by the publisher. The late 1930s was in general busy with travel for Auden, setting the stage for his final emigration from England (to New York) at the beginning of World War II. In addition to Spain, he also visited Iceland during this period, and passed through New York on his way back from China. Incidentally, though this was clearly an important period for him personally and as a writer, Auden apparently didn't love the traveling all that much. Auden's recent biographer, John Fuller, has the following quote from Auden's diary from the trip:
This voyage is our illness: as the long days pass, we grow peevish, apathetic, sullen; we no longer expect, or even wish to recover. Only at moments, when a dolphin leaps or the big real birds from sunken Africa veer round our squat white funnels, we sigh and wince, our bodies gripped by the exquisitely painful pangs of hope. Maybe, after all, we are going to get well.
I think this is a great metaphor for a certain kind of traveler's despair. One could even extend it further: perhaps it's not just the voyage, but the traveler him or herself that is the "illness." One gets over the nausea of dislocation when motion finally stops.
On to the sonnets, which are, as a group, rather tough going. The strongest individual poems in terms of unity of theme and coherence are the first and last, and neither of the two are directly about China. Indeed, it seems quite possible to read them as more about Auden himself than about the place he had visited. Take Sonnet I:
So from the years their gifts were showered: each
Grabbed at the one it needed to survive;
Bee took the politics that suit a hive,
Trout finned as trout, peach moulded into peach,
And were successful at their first endeavour.
The hour of birth their only time in college,
They were content with their precocious knowledge,
To know their station and be right for ever.
Till, finally, there came a childish creature
On whom the years could model any feature,
Fake, as chance fell, as leopard or a dove,
Who by the gentlest wind was rudely shaken,
Who looked for truth but always was mistaken,
And envied his few friends, and chose his love.
The slightly clueless character at the center of this poem recurs in the first ten or so sonnets. He begins as above -- a person who is always slightly off as regards his politics or his "station" in life. I read these lines as autobiographical and for the most part self-deprecating, though there is a glint of Auden's pride in the gentle phrasing of the last line: "And envied his few friends, and chose his love." As the sonnets progress, he grows older, becoming depressed and less lovable (Sonnet V: "unwanted/ Grown seedy, paunchy, pouchy, disappointed,/ He took to drink to screw his nerves to muder"), before finally achieving a kind of regeneration with a seemingly symbolic boy-figure (Sonnets IX).
The China context, hinted at in Sonnet X, only really comes to the fore in Sonnet XI, with also seems to come closest to a kind of Orientalism. In the vein of many other Auden poems responding to War from the late 1930s, Sonnet XI is a strong injunction to joy and love against the gathering darkness of militarization. Here are the final lines of that sonnet:
History opposes its grief to our buoyant song,
To our hope its warning. One star has warmed to birth
One puzzled species that has yet to prove its worth:
The quick new West is false, and prodigious but wrong
The flower-like Hundred Families who for so long
In the Eighteen Provinces have modified the earth.
The last two lines clearly refer to China (on "Eighteen Provinces," see Wikipedia, and skip down to "The Term in Chinese"; "Hundred Families" refers, I believe to a medieval Chinese text called The Surnames of a Hundred Families). But theme of venerable Chinese tradition and "the quick new West" is fleeting; I don't see it recur in the other poems, most of which focus more on the ambivalence of the British presence in China. See, for instance, the opening lines of Sonnet XVI:
Our global story is not yet completed,
Crime, daring, commerce, chatter will go on,
But, as narrators find their memory gone,
Homeless, disterred, these know themselves defeated.
Who exactly Auden is referring to when he says "our"? The most obvious first reading is the English nation, but subsequent lines in the poem raise the possibility that he means specifically the overseas British, such as he encountered in the British colony of Hong Kong. And it might even be more specific (or more intimate) than that, as the "we" becomes "they" as the poem develops. "They," whose vision of the world has been rendered obsolete:
their doom to bear
Love for some far fobidden country, see
A native disapprove them with a stare
And Freedom's back in every door and tree.
"Freedom's back" is another phrase to puzzle over. A postcolonial reading might focus on the frontal aggression of the stare with which the Englishman is met. But freedom (presumably of the native) is something he can't quite access: it turns its back to him. (There is also, I would speculate, a possible gay subtext here: disapproval might also be a reference to the attitude towards homosexuality he encountered -- and I'll leave "freedom's back" to the reader's imagination.)
Several of the more China-themed sonnets invoke war and tragedy, but only Sonnet XII specifically alludes to genocide: "For we have seen a myriad faces/ Ecstatic from one lie/ And maps can really point to places/ Where life is evil now./ Nanking. Dachau." Note Auden's invocation of the "lie" of political orthodoxies, as contrasted to the truths of modern war represented by "Nanking" and "Dachau."
Ultimately, I don't find a coherent argument to Auden's Sonnets from China. The sympathy for the Chinese victims of the Sino-Japanese War is real, but hardly central thematically. A general tone of mourning and loss of place prevails, but it's hard to say whether that loss is Auden's personal alienation from English life, or a more generalized expression of political dislocation (linked to both British colonialism and its imminent entry into a new world War). Quite possibly, it's both, mingled together ambiguously.
Auden ends the sequence with a move towards Edwardian Liberalism and E.M. Forster: "Yes, we are Lucy, Turton, Philip: we/ Wish international evil, are delighted/ To join the jolly ranks of the benighted/ Where resason is denied and love ignored." (Incidentally, John Fuller, in his 2000 biography of Auden, argues that Auden probably meant "intentional," not "international" evil -- following a line in Forster's Where Angels Fear to Tread -- and that this may have been an error of the compositor.) Against loveless spite is an ethos of human decency, personal intimacy, and friendship. If that is Auden's point, one wonders about the real value to us of these sonnets today; perhaps he said it better elsewhere?
Further reading: One scholar who has been working quite a bit on Auden's China sonnets is Stuart Christie, of Hong Kong Baptist University. He has an essay called "Orienteering," which is available here (PDF). I find it helpful. A more recent essay appeared in the October 2005 issue of PMLA (for those who have university subscriptions). I think the earlier essay is the better of the two.
(And a note about online access: I've only quoted bits and pieces of the sonnets here -- trying not to trample too much on 'Fair Use'. For those who don't have access to a volume of Auden, I believe all of the sonnets can be accessed through Google's cache.)