Attacking A King That Has Lost the Right to Castle

     This is the title of a chapter in Vladimir Vukovic's classic The Art of Attack in Chess. He wrote that this situation arises when the K is no longer able to castle or has been driven from the castling area, adding the warning that just because the K has lost the right to castle does not necessarily always justify undertaking an attack aimed at mate. For an attack of this kind to be feasible the K must be exposed and vulnerable.
     The pursuit of the K is not always successful so a player undertaking such a pursuit has to be careful that the fleeing K does not elude him. To this end, pursuing the K by endless checks may actually be detrimental to the cause. Sometimes spinning the mating net by the means of quiet moves is necessary. That's what we see in the following game. Smyslov's taking of his time to build the net takes precedence over the pursuit of Florian's King.
 

Florian

    Tibor Florian (1919-1990) was born in Budapest and was Hungarian champion in 1945. He won 1st prize in Belgrade 1948. Florian was awarded the IM title in 1950. Around 1960 he became very active in chess organization both in Hungary and in the FIDE and was an early coach of the Polgar sisters.     
     In the book Genius in the Background by Tibor Karolyi and Nick Aplin the authors tell that in 1944 Florian and another master, Laszlo Lindner (a fixture in Hungarian chess for over 50 years), were sent to a concentration camp in Yugoslavia where they kept their sanity by playing chess together. Near the end of the war the Germans arranged train transport, ostensibly back to Hungary, for the prisoners, but the train was stopped at one point and the occupants were forced to march back towards the Third Reich; few survived the march. Lindner and Florian forgot to board the train, being distracted by a game they were playing and as result, they survived the war.