mobilization

Van Cortland (or Van Cortlandt) Park, in the North Bronx, scene of mobilization and training camps for soldiers headed to the Mexican Border in June, 1916.
"VAN CORTLANDT PARK NOW A MILITARY CAMP/Artillery and Cavalry Commands AssembleThere to Await Marching Orders" N.Y. Times, June 22 1916
query.nytimes.com/mem/archive-free/pdf?res=F30D17F63A5B17...
See also

Locatie waarschijnlijk het Schuttersveld (op de achtergrond molen De Valk)

Location, indeed, most likely, the 'Schuttersveld', with in the background the 'Marislaan'.
Affirmative that the windmill in question is the, still existing and now museum, 'Molen De Valk'.

The churchtower left from the middle is of the 'Marekerk'.

The building at the left hand side should be, the 'Leidsche Coöperatieve Melkinrichting 'De Landbouw' ' (Milk factory), established 1879, at the 'Rijnsburgersingel' number 23.

Have a look at the following picture, from 1904, from the Leiden Regional Archives and compare yourself:

www.leidenarchief.nl/index.php?option=com_memorix&Ite...

and

www.leidenarchief.nl/index.php?option=com_memorix&Ite...

They look to be from the London Scottish, 14th (County of London) Battalion, The London Regiment (London Scottish) of the Territorial Army, so this might have been taken at a pre-Great War Summer camp.

strong bunch of men to thro the chapp so high ,wounderfull captuer/capture

fantastic!

WOW- did he fall from an aeroplane!!!! john..

Fabulous!