<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-11-03</periodOfReport>

    <issuer>
        <issuerCik>0001583513</issuerCik>
        <issuerName>Global Defense &amp; National Security Systems, Inc.</issuerName>
        <issuerTradingSymbol>GDEF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001326389</rptOwnerCik>
            <rptOwnerName>Polar Asset Management Partners Inc.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>401 BAY STREET, SUITE 1900, PO BOX 19</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>TORONTO</rptOwnerCity>
            <rptOwnerState>A6</rptOwnerState>
            <rptOwnerZipCode>M5H 2Y4</rptOwnerZipCode>
            <rptOwnerStateDescription>ONTARIO, CANADA</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001590457</rptOwnerCik>
            <rptOwnerName>Polar Multi-Strategy Master Fund</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O POLAR ASSET MANAGEMENT PARTNERS IN</rptOwnerStreet1>
            <rptOwnerStreet2>401 BAY ST., SUITE 1900, PO BOX 19</rptOwnerStreet2>
            <rptOwnerCity>TORONTO</rptOwnerCity>
            <rptOwnerState>A6</rptOwnerState>
            <rptOwnerZipCode>M5H 2Y4</rptOwnerZipCode>
            <rptOwnerStateDescription>ONTARIO, CANADA</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-11-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>44000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.63</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>755609</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Polar Asset Management Partners Inc. (&quot;PAMP&quot;, f/k/a Polar Securities Inc.) serves as investment manager to Polar Multi-Strategy Master Fund (f/k/a North Pole Capital Master Fund), a Cayman Islands exempted company (and together with PAMP, the &quot;Reporting Persons&quot;) and has investment discretion with respect to the securities reported herein which are held by PMSF. The Reporting Persons disclaim beneficial ownership of such securities, and this report shall not be deemed an admission that any reporting person is the beneficial owner of the securities for the purposes of Section 16 or for any other purpose, except to the extent of the Reporting Persons' pecuniary interest therein.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Robyn Schultz, Chief Compliance Officer</signatureName>
        <signatureDate>2015-11-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
