Temptation: 1. bxa5?! thr. (2. Sf2+ etc., mainplay) Th8!! See below

1. e7!! (2. Sf6+ gxf6 3. Le6+ f5 4. Lxf5+ Kg5 5. Lxc2+ Kg4
6. Lxd1+! Dxd1#, unexpected direct mate)

Black has three options for sabotaging the "Almost-Rundlauf"...

Mainplay:
1. - Ta6)
2. Sf2+! gxf2
3. Th4+! Kxh4
4. Df4+ Kxh5
5. Txb5+(!) Txb5?? Kxg6
6. Dg5+! hxg5# Unexpected vertical battery-mate

The following variations show groundline-battery-mates:    

1. - dxe3 (6. - e2!!)
2. De6+ Kf4
3. Sc3!! - and against the announced continuation
4. Sd5+ Kg5
5. De5+, retour! Kg4 
6. Sxe3+ nothing helps anymore; Sxe3#
Note: 3. - Kg5(?), allowing to play Sd5/De5 also in reverse order, is no defence, insofar clearly irrelevant.

Subtle extra, "a bit shorter",
1. - d3 (5. Lxc2??)
2. Txg3+! Kh4
3. Th3+, retour! Kg4
4. Th2, silent hattrick-finish; ~/dxe3??
5. Sf2+ Sxf2# 

After 1. bxa5? Th8(!) the mainplay-modification 2. Sf2+ gxf2 3. Txg3+ Kh4 4. Df4+ Kxh5 5. Tg5+ hxg5 6. Dxg5+ Kxg5+ is failing because of 7. Txh8...(!) → the second, indispensable function of wTb8!