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...

Blimey! They're so young! I can't help but wonder how many (or rather few) of these young men returned to Britain alive.

Oh, that is the saddest picture I think I've ever seen. How many of those young men died?

stunning biziare photo

A vivid reminder that England sent it's upper crust to fight this war. How different things are now (especially in the US where the armed forces are comprised primarily of poorly educated kids from poor families).

Are these not the infamous 'The Eton Rifles' and is it not more likely that these were the ones who sent the 'oiks' over the top?