If the Colle-Zukertort were a make of car, selling it would be a headache.  The difficulty comes not from a lack of value, but rather from a lack of audience.

The Colle-Zukertort, whose basic scheme is pictured above, does not capture the Dangerous, Dubious, but Fun market of the Smith-Morra or Blackmar-Diemer Gambits.  It is not a Jeep.

Nor has it found a foothold in the large beginner/club level populations that its simpler kid brother, the "normal" Colle, enjoys. It is not the first choice among those whose budgets and needs are better met by a sturdy golf cart.  Sadly, when these same players decide to "trade-up," they don't give the Colle-Zukertort more than a passing glance.  To their c3-Colle eyes, the bishop on b2 just looks dumb, like an elevator in an outhouse or a hood ornament on a Yugo.

Thus, it's not too surprising that little literature devoted to the C-Z exists.

Books from White's side either package it as part of a repertoire (which makes sense) or couple it with the c3-Colle (which doesn't).  Not counting Soltis' 102-page effort, there was no book dedicated to just the C-Z until this year!

Books from the Black side, of course, show even less respect. Seeing a single line in a repertoire book is not very useful if an improvement is found or if your personal repertoire is not compatible with the line suggested.

I hope the key points below help players on both sides to better understand this wonderful opening.  Perhaps my comments on the white side can pique the interest of queen-pawn players, and my comments on the black side can lead you to defenses that fit your repertoire and generally increase your confidence so you are not depending solely on a supposed "silver bullet."

Key 1: Know What Makes the C-Z Tick

The Zukertort is based on a single idea - Black has trouble developing his Q-bishop in Q-pawn games.  Everything from color complex control to targets to plans orbit this central point.  It would be hard to overstate how good a job the C-Z does of leveraging this idea and its many (sometimes nuanced) ramifications, but suffice it to say that the C-Z crumbles like under-cooked terra cotta in your co-worker's office chair if Black can find a use for this bishop.

For White this means you must be alert to those move orders where Black has not shut in this bishop.  You should also be at least dimly respectful of the annoying lines where Black plays an early ...Ba6 (as former Irish National Champion Eugene Curtin once did to me).  If Black plays this bishop to g4 or f5, you simply cannot continue in the natural Zukertort scheme.  These deviations occur in practice with greater frequency than all "main lines" put together.

Black players are in the pleasant position of benefiting from this point even if they have a repertoire not naturally amenable to an early Q-bishop sally.  As is often the case, "the threat is stronger than the execution."  If at all possible, Black players should choose a move order that keeps alive the option of ...Bf5 or ...Bg4.  1.d4 Nf6 2.Nf3 d5 3.e3 c5 and 1.d4 Nf6 2.Nf3 d5 3.e3 c6 can be very awkward for the unprepared White player to address.  Even 1.d4 Nf6 2.Nf3 d5 3.e3 Nc6 is more formidable than you might expect.

Key 2: Understand the Cosmic Exchange

White's Caissa-granted gift is the initiative.  In the C-Z we see White exchanging this for an ensemble of other goodies.  Unlike the "normal" Colle, White gets decent development for all his pieces.  He can also be reasonably assured of center stability and king safety.  Finally, he hopes later to extract some gain from Black's difficulty in transferring pieces from his Q-side to his K-side due to the pawn structure and Black's f6-knight.

Unlike many other openings, Black does not suffer from a particular lack of space.  He can have more or less all the space he wants...but only on the Q-side!  He also does not have to deal with any particular early skirmishes because White is not threatening anything.

Black should leverage this lack of pressure by staying flexible until White has committed with 3.e3, the albatross of the Colle System which voluntarily hems in the Q-bishop.  Almost any defense becomes better if Black bides his time until White has bitten that bullet.  For example, 1.d4 Nf6 2.Nf3 d5 3.e3 g6! used to be the single most problematic of all "anti-Colles."  Black fools White until committing before transposing to a Grünfeld.

Similarly, 1.d4 Nf6 2.Nf3 d5 3.e3 Bf5 is better than the Baltic Defense, 1.d4 d5 2.Nf3 Bf5.  And 1.d4 Nf6 2.Nf3 d5 3.e3 c5! is stronger than 1.d4 d5 2.Nf3 c5 (though both are rather good) while 1.d4 Nf6 2.Nf3 d5 3.e3 Bg4 is better (but by less than most think) than the Reversed Tromp: 1.d4 d5 2.Nf3 Bg5.  Note in this last line that if White follows most manuals and plays 3.Ne5 Bf5 4.c4, expecting 4...e6?!, then after 4...f6! 5.Nf3 (Qa4+ doesn't go anywhere), it is White rather than Black who is down a move on a more normal order since the pawn on f6 is actually pretty useful.

These "commitment problems" make some White players be selective in their use of the C-Z.  Yusupov is one example.  He plays the Colle-Zukertort much more often when Black plays ...e6 early.  Colle himself did the same.  On the other hand, you could just learn the antidotes to these lines, much as a Najdorf player has to have an answer to 3.Bb5+.

White has a terrible record from here, though that might have as much to do with the relative strengths of the players involved than with the position itself.  In any case, from a practical perspective this position is very distasteful because White's temporary retreat means Black can play ...Nd7 or even ...Ne8 without fear of White drumming up an attack while the knight is displaced.

Key 3: Know the Crucial Squares!

To maintain the advantages described in the last section, White must pay special attention to certain squares.  White need not control these squares necessarily, often it suffices to make sure Black cannot place a piece on them.

In particular, White will never want Black to put anything (pawn or piece) on e5 or f4.  Furthermore, Black should not be allowed to place a piece on d5 or c5.  Should Black gain traction on any of these squares, White's game may soon look and smell like two-year-old bananas.

White can thank his d4-pawn for preventing many of these options so long as Black has played d5.  Be careful should Black adopt, for example, a QID formation that delays ...d5.  If Black gets ...Nc6-b4-d5 in, White can be confident his opening efforts have failed.

Because the d4-pawn is so important to White, he should never advance it or allow it to otherwise become displaced without good reason.  Such d-pawn departures can be a critical element or harbinger of an attack, but it can also be a visa into "How Did This Happen" Land.

For example, 1.d4 Nf6 2.Nf3 d5 3.e3 e6 4.Bd3 c5 5.b3 Nc6 6.O-O Be7 7.Bb2 O-O 8.Nbd2 b6 9.a3 Bb7 [diagram] is loosely considered the mainline for the classical variation:

Preventing ...Nc5 is harder than it seems since after 13.b4 Qc7!  Black attacks e5 while threatening ...a5, which both hits b4 and itself threatens ...Ba6.  Both f4 and Nf3 remove a natural way of adding support to the b4-pawn via Qg4!?, and Black has more than adequate defense against an attack based on Qh5.  [Though an immediate 13.Qh5 played as a finesse (13...g6 14.Qe2) is a reasonable idea, giving you a weakness to use and making the imminent loss of your bishop more palatable since the f7-g6-h7 pawn formation rather blunts that bishop anyway.]

Key 4: Understand the Lever

Since White restrains his c-pawn and neither White nor Black is likely to advance their e-pawns soon, the c5-d4 lever represents the only tension in the central pawn complex.  The character of this lever is largely informed by the placement of Black's Q-knight.

If Black has played ...Nc6 , this lever is a "double-tailed coin" for Black.  He wants to exchange on d4 to get play down the c-file, but doing so opens the e-file for White.  In particular, a queen on e2 or a rook on e1 can now hit e4 and e6.  The former is useful since White typically wants to keep two pieces on e4, so the rook's presence frees the d2-knight for more ambitious initiatives.  Hitting the e6-pawn is useful as Black has problems maintaining defense of this immobile pawn.

Nor can Black simply bide his time and open the c-file after he has established a knight on e4.  A famous example is the line 1.d4 Nf6 2. Nf3 d5 3.e3 e6 4.Bd3 c5 5.b3 Nc6 6.O-O Bd6 7.Bb2 O-O 8.Ne5 Qc7 9.f4 b6? [diagram]

10.Nxc6! Qxc6 11.dxc5 Bxc5?? (11...Be7 lets Black struggle on a pawn down with some compensation) 12.Bxf6 gxf6 13.Bxh7+! [diagram]

This is the type of position a C-Z player puts as his computer display background.  There is no stopping mate with the queen and rook.

If Black has played ...Nbd7 instead, neither side is likely to exchange.  White has no interest in allowing ...Nxc5, and Black's only real play comes from establishing a knight on e4, an undertaking that becomes far more difficult if White has an open e-file.  Indeed, White is advised to snap that knight off immediately, after which the game takes on a very different character.

Final Thoughts

Given the content of our little discussion (and by discussion I mean "monologue"), you may wonder why on Earth I would even play the C-Z myself, let alone write a 256-page book from the White side of it.  It is true that there are lots of monkey-wrenches to be thrown at White, but in many of these cases there are strong and interesting counter-refutations, including some true gambits where White has full compensation and then some.  For example, one line I advocate after one of these monkey-wrenches could easily lead to the following:

Yes, there are several ways for White to go wrong if he plays the Colle-Zukertort in a lazy fashion or without being aware of its deeper nuances.  But I would say the same is true of any opening worth playing, and I'm hopeful that the CZ will come into its own as something that is "offbeat, but worthy of respect."  Perhaps it will join the ranks of the Benko Gambit and the Chigorin, both of which might have looked odd at first but eventually have shown their value.  Could the C-Z be the Prius of Chess' 21st century?
 

[David Rudel is a published mathematician, winner of the International Contest in Mathematical Modeling, and Senior Editor at ExploreLearning.com.  He is the author of Zuke 'Em: The Colle-Zukertort Revolutionized, published by Thinkers Press.  Excerpts and information at www.zukertort.com.]