Backbone + Webpack `Uncaught TypeError: _.create is not a function`, underscore not loading? - backbone.js

Question

I'm using webpack for the first time. When requiring backbone, it seems to not be loading underscore properly, since I'm getting the error Uncaught TypeError: _.create is not a function in backbone.js:1892 in my browser.
main.js
'use strict';
import Backbone from 'backbone';
Backbone.$('body'); // Doesn't error
Backbone.View.extend({}); // Gives error
My webpack config can be found in this boilerplate repo.
└─┬ backbone#1.3.3
└── underscore#1.8.3
*Update* When I use backbone v1.2.3, it works fine. v1.3.0+ causes this error.

Answer 1

Turns out it was an issue due to npm3's method of loading dependencies, combined with my webpack config.
I was using a directory for the modulesDirectories property.
modulesDirectories: [
path.join(__dirname, 'node_modules')
]
Since npm3 loads dependencies in a flat way (all at the root node_modules dir, and version conflicts get put into the module's directory under a node_modules subdir, webpack was always importing underscore 1.7.x (a dependency of another module in my project) instead of the 1.8.3 that was in backbone's subdir.
Downgrading to backbone v1.2.3 only worked because it was using the same version of underscore that my other dependency was using, so there was no conflict.
I removed the modulesDirectories completely, since it has a default. I could have also changed this to modulesDirectories=['node_modules'] to get the same effect.