Switchback

A switchback happens when one piece departs from a square and later returns to that square via the same path.  Switchbacks make for a striking visual effect.  

Moen, Kabe
Problemas 2018

#2

11 + 7

We'll start with one of my problems that features an unpin self-pin strategy.  There is relevant set play:

1...Rb8 2.Sb7
1...Ra8 2.Sa6
1...Rxc5+ 2.Rxc5

However, this is not retained in the actual play.  Notice that the wBd7 can step away and make a threat along the b1-f5 diagonal but this action will also unpin the bS.  This determines where the wB must land, all the way at the edge of the board to provide for the oncoming check 1...Rxc5+ and now 4 variations follow from the newly unpinned bS including the switchback.

1.Ba4! (>2.Bc2)
   1...Sxc5 2.Bd7 (switchback)
   1...Sxd4 2.Sxd4
   1...Sf4 2.Sg3
   1...Sg5 2.fxg4

Also the check 1...Rxc5+ is now met by the threat 2.Bc2.  
   

Salazar, Francisco
Die Schwalbe 1968

#2

10 + 3

Here is a classic.  Notice that Black is in stalemate and it seems that White must unpin the bB.  

1.Se5? (-)
   1...Bh3 2.Ng4
   1...Bxe6 2.Sf3 
   1...Bxd3 2.Qg2
   but, 1...Be4!

1.Qg2! (>2.Qa2)
   1...Bxd3 2.Se5
   1...Bxe6 2.Qg5

Two switchback in each phase and the Salazar theme: Reversal of try move and variation mate. 

Shinkman, William
Tidskrift for Schack 1911

#2

4 + 3

Here is a personal favorite and an eye catching miniature that features some nice promotion play by Black.

1.Qf3! (>2.Qc3)
   1.Ke1 2.Bc3
   1.e1=S 2.Qf2
   1.e1=Q 2.Qd3
   1.Kxc2 2.Qxe2

Mansfield, Comins
Die Schwalbe 1961

#2

10 + 9

Mansfield offers three switchback from 3 different pieces and a true switchbacked themed problem.  As usual flight giving tries and key are thrown in for good measure.

1.Sdxe4? (>2.Rd4,Qd3)
   1...Qxa1 2.Sd6
   1...bxc5!

1.Scxe4? (>2.Re5)
   1...Qxa1 2.Sc5
   1...Kxe6 2.Qf7

1.Rcxe4! (>2.R4e5)
   1...Qxa1 2.Rc4
   1...Kxc5 2.Rc4
   1...Sxd5 2.R6e5

Mansfield, Comins
A. Bottacchi M.T., Sinfonie Scacchistiche 1973

#2

10 + 8

​More Mansfield magic.  This time the wK makes the switchback while giving a flight and sacrificing two pieces at the same time.

1.Ke7! (>2.Re5)
   1...exf5 2.Kd6
   1...exd5 2.Kf6
   1...Kxd5 2.Sf6
   1...f6 2.Qxe6
   1...Sf3 2.Qxd3
   1...Sc4 2.Qxc4

Notice the nice little change from the set play after 1...f6.
​ 

Kovacevic, Marjan
Belgrade Internet Tourney 2008

#2

5 + 13

Now on to the exquisite creations of possibly the greatest living two-move composer.  Marjan has composed more switchback problems than I can include in the blog, so it was an impossible task to pick just one.   I have selected three problems all in FIDE albums.  All three problems have a choice of battery formation with a switchback in each phase.  Also, take a look back at the battery play blog for another example and the article by David Shire in the March 2015 Problemist.  

​There is a battery to be formed on d5 but which should be the lead piece, the wB or wS?  Either one opens a bR line to defend and makes for a nice little switchback coupled with a shut-off mate after the bR crosses the battery line.  

1...c4 2.Rxd5
1...Bc4 2.Sxc4

1.Sxd5? (>2.Qa6)
   1...c4 2.Se3
​   1...Rb3 2.Sc3
   1...Bc7 2.Qxc7
   1...Bxd5 2.Rxd5
but 1...Bc4!

1.Bxd5! (>2.Qxb8)
   1...c4 2.Be4
   1...Rb4 2.Bc4
   1...Bc7 2.Qf8
   1...Bxd5 2.Rxd5

The white economy is superb.  Perfect unity and stunning changes.

Kovacevic, Marjan
Neue Zurcher Zeitung 2008

#2

8 + 9

Here is another battery creation wonder.  The bK has a flight at d3 with a set mate 2.Qxd4.  Notice the strong Black move 1...Rxg1 that creates a flight for the bK at f3.  This suggest a threat of Qf5.  

1...Kd3 2.Qxd4
1...Qf3 2.Rxd4

1.Sxd4? (>2.Qf5)
   1...Kd3 2.Sc6 (switchback)
   1...Qf3 2.Sb3 
but 1...c5 provides an excellent refutation

1.Bxd4! (>2.Qf5)
   1...Kd3+ 2.Be5
   1...Kf4+ 2.Be3
   1...Qf3 2.Bb2

Amazing play with a Zagoruiko (three different mates after the defenses 1...Kd3/Qf3) and a beautiful flight giving key that allows two cross checks.  So artistic.

Kovacevic, Marjan
Schach-Aktiv 2009

#2

11 + 9

One more that I could not resist.  This time the battery creation does not even require a capture.  Here we have a choice of masked battery creation.  A move to d4 will unpin the wS and threat the double check 2.Sb6.  Again there is meaningful set play.  

1...Rxd5+ 2.Bxd5
1...Sxe3+ 2.Sfxe3

1.Bd4? (>2.Sb6)
   1...Rxd5 2.Sd6
   1...Sxe3+ 2.Sdxe3
   1...Sxd5 2.Ba1 (what a switchback!)
   1...Sxe2 2.Qxe2
but 1...Bb4!

1.Sd4! (>2.Sb6)
   1...Rxd5 2.Qxc8
   1...Sxe3+ 2.Sxe3
   1...Sxd5 2.Sf5 
   1...Sxe2 2.Qxe2

Again we have a Zagoruiko theme with unpinning and lovely switchbacks - my favorite is the switchback in the try phase.