Table: blitz_stats
Columns: month_year
day_sorties_losses
night_sorties_losses
luftflotte_2_sorties
luftflotte_3_sorties
major_attacks
heavy_attacks

Question: How many heavy attacks did the 450 Luftflotte 2 conduct?
SQL: SELECT COUNT("heavy_attacks") FROM blitz_stats WHERE "luftflotte_2_sorties" = 450