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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2009-12-16</periodOfReport>

    <dateOfOriginalSubmission>2009-12-17</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001471038</issuerCik>
        <issuerName>GLOBAL DEFENSE TECHNOLOGY &amp; SYSTEMS, INC.</issuerName>
        <issuerTradingSymbol>GTEC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001476548</rptOwnerCik>
            <rptOwnerName>Perl Andrew Damian</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1501 FARM CREDIT DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 2300</rptOwnerStreet2>
            <rptOwnerCity>MCLEAN</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>22102-5011</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001476535</rptOwnerCik>
            <rptOwnerName>Contego Systems LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1501 FARM CREDIT DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 2300</rptOwnerStreet2>
            <rptOwnerCity>MCLEAN</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>22102-5011</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001476550</rptOwnerCik>
            <rptOwnerName>Kende Holding kft</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ZICHY JENO U. 4</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BUDAPEST</rptOwnerCity>
            <rptOwnerState>K5</rptOwnerState>
            <rptOwnerZipCode>1066</rptOwnerZipCode>
            <rptOwnerStateDescription>HUNGARY</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001476549</rptOwnerCik>
            <rptOwnerName>Global Strategies Group Holding S.A.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>15 BOULEVARD ROOSEVELT, L-2450</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState>N4</rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription>LUXEMBOURG</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3803274</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">In a Form 4 filed December 17, 2009, it was reported that A. Damian Perl, as a non-employee director of the Issuer, was granted 3,845 restricted shares by the Issuer on December 16, 2009, with such shares scheduled to vest in three equal, annual installments beginning on the first anniversary of the grant date. This amendment is being filed to reflect the fact that instead of receiving such restricted shares, A. Damian Perl will receive cash in an amount equal to the value of such restricted shares, as determined under FAS 123 as if such shares had been granted on December 16, 2009.</footnote>
        <footnote id="F2">These shares are owned by Contego Systems LLC (&quot;Contego&quot;). Contego is wholly owned and managed by Kende Holding kft (&quot;Kende&quot;). Kende is 99.98% owned and controlled by Global Strategies Group Holding, S.A. (&quot;GLOBAL&quot;). GLOBAL is controlled by A. Damian Perl.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Lisa Broome, Attorney-in-Fact for A. Damian Perl**</signatureName>
        <signatureDate>2010-03-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Lisa Broome, Attorney-in-Fact for Contego Systems LLC**</signatureName>
        <signatureDate>2010-03-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Lisa Broome, Attorney-in-Fact for Kende Holding kft**</signatureName>
        <signatureDate>2010-03-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Lisa Broome, Attorney-in-Fact for Global Strategies Group Holding, S.A.**</signatureName>
        <signatureDate>2010-03-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
